My .02s are that it may be helpful to know who you're going to be doing work for...
ASP/.net - Government and Private sector companies with deep pockets (most of Fortune 500), and non-profits that are MS centric.
JSP - Specialized technology firms, contractors to the Feds or Military sectors, usually very large & and long established companies (ie. Gieco) and a lot of firms in the wireless/PDA world.
PHP - Non-profits, startups, small/mid-sized firms, ISPs, technology innovating firms, new media firms, large universities, cool kids, and the rest of the entire world.
Disclaimer, these are just my personal experiences doing web dev work here in Washington DC. You results may vary... widely.