I have extensive notes and introduction as part of the Bio720 class and I suggest starting there.
If you are just starting out.. suggested course of action... intro book. CSE845 notes and screencasts...ZOL851.... Bolker, R Book, R in a nutshell, Hadley's book.
Introductory Statistics with R - Peter Dalgaard (needs MSU proxy access)
Hadley Wickham's Avdanced R book
The R book (note - needs MSU proxy for access)