There's been a recent spike of activity from people posting Microsoft interview questions online. Here's some links:

• Chris Sells' Questions for Testers, complete with some interesting SDE/T questions
• Aaron Boodman's Interviewing at Microsoft. Good listing of SDE questions, which are usually touched upon (but not concentrated on) for Test positions
• Kiran Bondalapati has an older page with a lot of goodies here. These are fairly generic for all the Microsoft technical positions.

One important thing to note: if you're interviewing for a technical position, don't be surprised if you are asked a category of question that doesn't fit the one for which you are applying. It's not uncommon for Devs to be asked Test questions, for Testers to be asked Design questions, or for PMs to be asked Dev questions. Be prepared for those curveball questions! :-)