Very useful thread; if anyone has any comments about finding mentors, it'd be really appreciated. Are professors really that receptive to email?
I found my mentors through interest groups and emailing faculty I had worked with as a TA. The faculty who get involved in interest groups get into that because they want to help students out and a lot of them will gladly take on students for research ime. Also, some of the interest groups at my school have sign up sheets to connect students to faculty members for research.