A company called AskSam has compiled transcripts of Obama's speeches, dating back to 2002. The collection is not exhaustive: post-election radio/YouTube addresses aren't included, for example, and the latest speech on the AskSam site is from Inauguration Day. Still, at 220 speeches this site will probably be a handy tool for the first wave of students who'll be doing projects on our new president and his rise to power.
The speeches can be browsed and read online. But AskSam offers a (free) viewer that once downloaded, treats the speeches as a database of sorts and allows textual analysis by a variety of means.
It's unclear whether the Obama speech site will grow on AskSam, so obviously, students will need to be pointed to White House Briefing Room materials, too.