Second the decent charger recommendation, for years I used walmart quality chargers and was disapointed when my batterus would die when I needed them most. For the $30 wasted on a low quaility charger you can get a maha c401fs for $40.

Low self discharge NiMH is the way to go, Sanyo eneloop are some of the best out there but there are many others.
with the low self discharge batteries on the market there really isn't much need for non rechargeable batteries any more.

WRT rechargeable and lithium, lithium are not rechargeable, lithium ion are and they are not in standard sizes like AA and such. Be careful buying devices which use lithium ion (gps, camera, etc) when there are aa powered available, you then have to have a charger dedicated to that device and plan to replace the batteries ever few years since lithium ion have a shprt lifespan compared to other technologies.

Nicad has their place, if you have a simple trickle charger like in those little solar powered yard lights or cordless phones a nicad will last longer since none of the other technolies are as tolerant of the constant charge.