If you stick with AA, consider getting a faster charger. I've had a LaCrosse BC-900 for a while, and picked up a BC-700 to keep at work.

For under $100, one option is to pick up inexpensive 2xAA flashlights like these: http://www.shiningbeam.com/servlet/t...-235-II/Detail Stick them to your bars with TwoFish LockBlocks, maybe put one on your helmet with a couple decent rubber bands, and you're still in familiar AA territory. But you'll need to change the cells for fresh ones fairly frequently.

Another option is to invest in 18650 Lithium-ion cells and a charger, and then you can choose from all sorts of 18650-powered lights. This one's OK, and you could probably get two 16-mile commutes on one cell: http://www.shiningbeam.com/servlet/t...4-II-R5/Detail I have the previous version, where "Low" was not as low, and it appears to do about 5 hours on High before it starts to dim noticably.

If you decide to go 18650, make sure you get protected cells for safety. I use these:
http://www.batteryjunction.com/2600pcb-18650.html

and this charger:
http://www.batteryjunction.com/wf-139-.html

Batteryjunction also carries the beefed-up Cycloblock, but the price is pretty beefed-up too:
http://www.batteryjunction.com/twofish-cycloblocks.html



Oh, and you could also consider a dynamo-powered system. Peter White Cycles has Sanyo dynohubs for $37, and you can get an inexpensive headlight that has a standlight (stays on for a while when you stop) for about $47: http://harriscyclery.net/product/bus...light-3200.htm But you'd also need to get your front wheel rebuilt around the new hub, so that isn't within your stated budget.