1. You can straighten a bent alloy chainring by tapping it with a large rubber mallet, while still on the cranks.
2. Never give up on seemingly broken Shimano brifters or trigger shifters without first flushing them with a half can or so of WD 40 (lots of info on the fine points of this technique in the forum archives)
3. The Barkeeper's Friend product mentioned earlier also comes in a thick liquid form. I've found it at Lowe's in the cleaning products.
4. Don't destroy your chain tool trying to remove a badly rusted chain. You can get a motorcycle chain breaker at Harbor Tools for under 20 bucks.