Try the University Laboratory for Animal Medicine. They always have jobs in the Daily and they pay well too.

The job is mind numbing, though!!! 

It really depends on your school, and hence, your contacts.  I am a part of the College of Engineering, as are many of my friends, and anyone who wanted a summer job pretty much got one (though maybe not the first one that they applied for).  Talk to professors that you like, or try to use the friend network to explore other schools on the campus.

There is also a link on the umich.edu website where professors and other faculty post "help wanted" ads.