Costco visitor here. Those 48 x AA packs for about $9 or $10 are great!

I attempted to standardize batteries a while back but gave up. I try to keep lots of AA (alkaline + lithium), AAA (alkaline + lithium), and 123-sized cells (lithium) on hand.

You're also gonna need a way to keep batteries together and protected. Here are a few web sites with cases and whatnot:

http://www.inanycase.com
http://www.tadgear.com
http://www.countycomm.com
http://www.toolsaviation.com

What kind of batteries are those for?

Some higher end flashlights use the cr123

Just thought I'd throw in a decent source for the coin cells: digi-key. The 2016/2032 cost 30-40 cents each there for Panasonic, they seem as good as the others. Many national stores charge $5-6 each for them in these parts.

Anybody tried the Stramlight-branded 123s? I bought a bunch but haven't tried them yet. They were real cheap (compared to my usual Energizers), so I'm wary.

Digikey and mouser are pretty good for anything like that. coin cells, odd sized and solder tab NiCad, etc. If your rebuilding an old battery pack they can spot weld the cells together for you.

Another one for custom pack building is cheapbatterypacks.com. Good prices, good quality. I got them to build custom packs for my radios/drills/etc. with more modern cells than the Ni-Cds they came with (and are still often sold with). Not that I'm recommending any rechargeable for any survival situation, but for general use...

Low self discharge NiMH are my primary survival gear batteries now (Sanyo Eneloop). They don't have the self discharge problems that traditional NiMH have or even that NiCad has.
Then a good quality charger that can be powered from 12v so it can work in my truck or from solar or whatever.

I have used Streamlight 123's for a while now and have always had good results with them. Last weekend I bought 12 for $20 at a local gun show. The Surefire 123's were 12 for $24. I have been told, but have not been able to confirm, that the Streamlight batteries are manufactured by Duracell. I have always been happy with mine. I stock up at gun shows because that's where I find the best deals on them.

Good tip! It was the self-discharge aspect that made me say that.

Yeah, I keep a solar panel and charger in the car. Because I don't trust the NiMH I usually use for some stuff. I have not seen those Eneloop sold around here...may have to dig.

I had went away from re-chargeable for a few years due to self discharge issues as well.
The best price on eneloop is the $7.99 for 4 AA at HHGreg. Then other stores like Circuit city have been reported to have them around $11.99 and $11.99 or 19.99 for 8 seems to be the average online price.
There are others like them, Rayovac hybrid, Uniross hybrios, nexcell something or other.
Also a decent charger helps out as well. I found out the charger I gor from walmart would only charge the batteries to 70 something percent of a full charge so I was loosing a lot off the top right there. I finally bought a $40 MAHA and it has recovered some of my old NiMH to the point where they are useable again in secondary stuff.

The other advantage with the low self discharge is you can charge them ans have them waiting, no one hour chargers or 15 minute chargers needed, just have a set already fully charged and waiting.