Paul Graham discusses some "Frighteningly ambitious startup ideas" in a post on his blog (based on a speech he gave which is available here). He wants someone to replace 1)Google 2)email 3)universities 4)Hollywood 5)Steve Jobs 6)code optimization and 7)doctors.
For #1, he suggests a startups create a search for hackers, though I think it might be easier to focus first on certain high-revenue categories that Google doesn't do so well at. Both #1 and #7 sound very difficult, I'm not sure if a startup will be able to solve them, but there are larger companies (like IBM) which are making progress in those areas.
For #2, I don't know if email will be replaced anytime soon, but I assume more features will be added to it to help people manage its magnitude. Gmail and Hotmail already both have some features to help with this, and I assume such tools will improve.
#3 is an area I am especially interested in. I don't know if universities are about to disappear, but I think the traditional lecture model will be upended.
Another interesting link from today: Job Growth and Loss (LinkedIn). Looks pretty good for Tech stuff. Of course, some of the shrinking areas may be rebounding now, while some of the growing ones may be in a bubble (see the greenest one on the chart).