http://www.pbs.org/wgbh/evolution/library/04/index.html [Evidence for Evolution]
http://www.talkorigins.org/faqs/comdesc/ [Talkorigin's 29 Evidences for 'macro'-evolution]
http://www.talkorigins.org/faqs/faq-speciation.html [Observed Instances of Speciation]
http://www.talkorigins.org/faqs/speciation.html [More Observed Instances of Speciation]
The work of Herman Muller who was a pioneer in radation bombardment experiments:
http://nobelprize.org/medicine/laureates/1946/[nobelprize.org] (he received the Nobel prize for inducing mutations through radiation bombardment)
For debunking of other creationist pseudo-science nonsense (eg. 'evolution violates the 2nd law of thermodynamics') see http://www.talkorigins.org/origins/faqs-qa.html and the rest of that site.
Scientific America: 15 Answers to Creationist Nonsense http://www.sciam.com/article.cfm?articleID=000D4FEC-7D5B-1D07-8E49809EC588EEDF&ref=sciam
Talkdesign (Talkorigins sub-site): Critically examining 'Intelligent Design': http://www.talkdesign.org
Millenium Project: Answers to creationist nonsense: http://www.ratbags.com/rsoles/creationism1.htm
Arguments creationists should not use from a Creation 'science' site that pushes the idea that the earth is only 6000 years old: http://www.answersingenesis.org/home/area/faq/dont_use.asp (even they advise people not to use the '2nd law of thermodynamics' argument)
Various links to newsgroup posts and various articles which give examples of evolution which have been scientifically observed: http://groups.google.com/group/alt.atheism/browse_frm/thread/8bd1fcfa82e3609b/0e8757e24bda17dc#0e8757e24bda17dc
Note: I have nothing against people believing that god created the world, personally I'd prefer to believe that god exists rather than not. However I disagree with people who falsely claim that these religious beliefs of their's are based in science or fact, that they should be taught as science in schools, that evolution is not a science or is a religion itself, that people who 'believe' in evolution (ie. science) are somehow immoral or anti-family (whatever that means) and so on.