I'm reading History at Sidney Sussex. We came top for History last year and have a pretty good reputation for the subject. Our DoS is Martin Ruehl, if you want to look him up. He says that Caius, Emma and Peterhouse are particularly strong for History too. I also went on open days at Selwyn, Newnham and Pembroke if you want to know more about those colleges. On the whole I wouldn't worry too much about the fellows at each college as you will receive tuition from all different colleges. My supervisors have come from Sidney, Peterhouse, Homerton, King's, Christ's and Tit Hall. The Director of Studies is someone you will have more contact with, however, so I can see why you would want to look them up in particular. Here's what I can tell you.
SIDNEY: Martin Ruehl (intellectual thought/Europe). An excellent teacher and very helpful. Always tries his best for his students. We also have Richard Partington (medievalist), the Admissions Director, who is very willing to answer questions and is actively involved in the GHP sessions run in college. Both are quite young.
SELWYN: David Smith (Stuart expert). Supremely nice. Ooh, or it could be John Morrill. He's good too.
KING'S: Stephen Alford (Tudor guru). The loveliest man in the faculty, really friendly and helpful. Young.
PEMBROKE: Paul Warde (EM Europeanist). The best lecturer in the faculty. Seems very nice, quite young.
TIT HALL: can't remember her name, but she is very helpful and generally very nice. Will push you hard.
PETERHOUSE: can't remember her name either. She's young and nice.
NEW HALL: again, can't remember her name. Has been very good.
NEWNHAM: Gill Sutherland. Will push you hard but is excellent.
Hmmm, I seem to think all the DoSes are nice. I guess that's their job! But anyway, if you have any other questions about History at Cambridge PM me. I'll get back to you ASAP, but my exams are 3-13 June so bear with me if I don't respond immediately.
In terms of colleges themselves, they're more alike than not usually. The easiest way to narrow them down is to consider size, age and location. I wanted a reasonably old, small, central college - Sidney fitted the bill! Open days are also a good idea. Pembroke, Selwyn and Newnham were very similar to Sidney (with the obvious exception that Newnham is women only) but Sidney had a different atmosphere that I could only pick up from the open day. Lots of people talk about colleges clicking, and that was true for me. Again, if you have any questions I'll do my best to answer them.