How can I charge my phone while cycling?
Three options that I know of:


AA cell phone charger (which you're already using) -- uses 2 or 4 AA's to recharge your gadgets.  I use an Energizer model to charge my GPS for rides over 12 hours.  Of course you need to carry enough batteries for the length of your ride.
Solar charger -- can be mounted on a handlebar bag, a rear rack or hanging from your pack and typically has mini-USB connections for cell phones etc.  No batteries required but won't help much on a rainy day.  I've seen a variety of these at local outdoors shops.
Dynamo hub charger -- this is probably the most expensive option, especially if you don't already have a dynamo hub.  I'd like one of these (already have the hub) but the AA charger has been fine so far.