While I agree that having more women in the computer industry would be a good thing, I have difficulty believing some of the claims that Pia makes. For example the claim that “[girls] are more career focused earlier in their school life“. I chose my career when I was about 11 years old  and several of my friends made similar decisions at similar ages. I would be interested to read anecdotal evidence from women in the computer industry about how old they were when they decided on their career and if their friends did the same, a reference to any research on this topic would also be useful. I tend to believe that boys are more career focussed at all stages of their life but have little evidence to support this idea. One fact that seems obvious is that the idea that “if you don’t succeed in your career then you can always marry someone who does” is almost non-existent among boys. It seems likely that such ideas have a statistically relevant affect on the focus on career of boys vs girls. Also the Australian Bureau of Statistics reports that the MEDIAN income for women is significantly lower than for men , I find it difficult to imagine that girls could be more career focussed from a younger age and yet get significantly lower pay (note the fact that it’s median not mean income is very significant as it removes the “glass ceiling” effect).
Phillip Greenspun writes about why there are so few women doing scientific research  and makes some good points about why scientific research is generally not well paid and therefore a university student would choose a career in some other area and suggests that it’s a macho thing that guys enter such competitive fields for relatively low wages. Maybe some women correctly assess the costs and benefits of a career in scientific research and then make the mistake of equating Computer Science to other branches of science.
But the median income suggests that although there may be some valid reasons for avoiding science that would only cover a small portion of the problem (the difference in median income can not be explained by misplaced attempts to maximise income).
One problem that is significant is the quality of school education for girls. Not only is there the issue that boys may crowd-out girls for some subjects that are supposedly traditionally for boys (such as all science) but even girls schools aren’t as good as they should be. Some time ago I was talking to a teacher at an all-girls school, the school was moderately expensive and parents were paying the extra money presumably to give their daughters educational opportunities that they might miss in a co-ed school. However the school did not teach hard maths (“Maths B” was the official name at the time) and only taught the easy maths (official name “Maths A” and unofficial name “Vegie Maths“) because they didn’t have many girls demanding it (which is probably difficult to measure if you don’t offer it as a reasonable option) and the girls who wanted to study it could always move to a different school. So the choice facing girls at the exclusive school in question was “skip the subject that is most useful for further studies in most science subjects” or “go to a different school and miss most of your friends“, this sort of decision would surely discourage some potential female computer programemers. Also I think that the difference between boys and girls in regard to studying computer science has a lot to do with the fact that given a choice between missing most of their friends and missing out on something related to computers would be a no-brainer for most boys. Paul Graham’s article about Nerds has some interesting points to make in this regard – maybe the problem is that girls aren’t Nerdish enough .
Pia also writes about parents and teachers advising children not do study IT because of a perceived lack of jobs. I think that the problem here is not just bad advice, but also a bad tendency to take advice. Someone who wants to study in an established field which changes little over time (law and accounting spring to mind) probably should take careful note of the advice that they are given – things haven’t changed much in the last few decades. But someone who wants to study in a field that changes rapidly and where every year has new and significant developments (of which the best example is the computer industry) should probably be quite skeptical of all advice – most advice about the computer industry concerns how things used to be not how things are. Finally when considering whether to accept advice you should consider who is offering it. For example advice from a hiring manager should be carefully noted (as the manager will tell you precisely what factors influence their own decisions on hiring). Advice from people who are successful in the industry should also be noted. Advice from a school career advisor who gets paid about 1/3 what any 25yo can earn in the computer industry should be entirely ignored. I wonder whether being hesitant to ignore advice is a problem for girls in this regard.
When I was in year 11 I had to take a subject related to career planning. It covered some things that were of minor use (such as writing CVs) and had an assignment of writing a fictional CV for yourself a few years after leaving university. I received bad marks for preparing a CV that involved changing jobs as companies went bankrupt or projects failed due to bad management, I was told that if your employer fails in the market it makes you look bad! However my fictional CV did bear some resemblance to what really happened…
In terms of what industries have jobs available, the best advice I can give students is to actively do some research of their own. It’s not difficult to get the jobs sections of some newspapers and do a quick scan to see how many positions are open in a field, and it’s even easier to do some searches on online jobs sites (which usually tell you how many positions posted in the last X days match your criteria). For example I just visited jobserve.com.au and found 1724 Engineering jobs and 5622 IT jobs advertised. If you compare this to the university intake (I visited the Swinburne university courses list  and found 25 IT courses vs 29 Engineering course) it seems that the ratio of Engineering graduates to jobs is not likely to be as good as that for CS graduates. Of course it may be that all the other universities have hardly any Engineering courses and balance the ratio out (but I doubt it). In any case this would be a good way of injecting some facts into a discussion of the relative merits of different career choices and avoiding it being an issue of parents/teachers not liking computers vs children liking them. Determining the relative pay rates of different industries is a lot more difficult (and requires a significant amount of work), some recruiting agencies publish statistics – but those stats only apply to the positions that they fill (which is a sub-set of the actual positions).
Finally as a piece of advice for children, try and find a job that you enjoy. If you earn $30K doing something you enjoy then you’ll probably be happier than if you earn $100K doing something you hate. Also if you enjoy your work then you will probably be able to take the extra steps needed to become successful – often it’s not a choice between having fun or making good money but a choice between fun and good money or the absence of both. If someone tells you to avoid doing what you love and instead do something boring for some unsubstantiated belief that there would be more money in it then be a nerd and tell them that their opinion is not relevant (it does tend to make teachers angry though).
-  http://pipka.org/blog/2007/10/09/getting-girls-and-gen-y-into-it/
-  http://etbe.coker.com.au/2007/08/23/the-start-of-my-computer-career/
-  http://courses.swinburne.edu.au/
-  http://www.abs.gov.au/AUSSTATS/abs%40.nsf/7d12b0f6763c78caca257061001cc588/96e08af8f4178a45ca257306000d4fd4
-  http://www.paulgraham.com/nerds.html
-  http://philip.greenspun.com/careers/women-in-science