Since I'm out of school, I decided to fool around with a really old 1965 sears-branded puch frame that's been in my basement forever. After trying to jam every spare wheel I have onto it, I went to find the rusty old turds that came on it originally, and discovered that they're 650's. I don't mind this because I'm a small guy (5'5"), but I originally wanted to do something goofy with this frame for fun, like build it up with some fat slicks and a coaster brake, but the spacing on the dropouts really limits my options.

So, does anyone have any suggestions as to different ways I could build up this frame?
(without spending a buttload)

sell it, buy a new one.
someone will buy it.
650 tires are hard to find when you really need one,
back when i owned a bike on 650c's

I bought them two and three at a time just so I know I had one with out having to order them or find them.

You can still get 650c wheels. Or 650b wheels. Or go a bit smaller with 26" wheels. Just how much clearance for fat tires do you have?

Lurk on eBay for used wheelsets. You might bid on THESE

Another set

Velocity makes 650c in their Aerohead, Fusion or Deep V rims. Any wheel maker can lace them up to some Formula hubs and off you go.