Probably the best resource is any university, just take an intro biology course. Similarly, nearly any good college level into bio textbook does a good job of explaining how evolution works.
The best online resource is probably the
talkorigins.org website - which is acknowledged by scientific organizations, schools, and museums as a great resource. They are especially useful in testing creationist claims, at
http://www.talkorigins.org/indexcc/ and also for the quick summary here:
http://www.talkorigins.org/faqs/comdesc/ Note that practically all scientists (including scientists who are Christian) support evolution, and most of the support for evolution in America comes from Christians.
For Christians in particular, I'd check out the
biologos.org website, and books like
and
Enjoy!
In Christ-
Papias