Yeah, I want a thickness sander but can't justify it right now. I have other fish to fry, priorities at the moment.
I'm very careful to read the grain and make sure I put the slabs through in the right direction and favor one side or the other once I have one good smooth side to work from. So far, no major explosions or tear-outs. Eventually I'll probably trash some really nice piece and then scrounge up some sander-cash.
So, yes Tim, what these guys are saying is good advice about a thickness sander. A decent machine can be pricey though. I've seen some scratch built, single-drum units built using a motor and roller... could be something to explore if you're handy and can find suitable parts.
Another option is the Safe-T-Planer from StewMac: http://www.stewmac.com/Luthier_Tools/Types_of_Tools/Planes/StewMac_Safe-T-Planer.html
There are other sources for this type device as well, I refer to StewMac because I've had good experience with them.
I've never used a device like this, but have read articles where folks seem to really like it. Very affordable, and is powered by a drill press (which even a small shop or budget may already have on hand).
Could be a good, affordable option to explore. Extremely versatile device, watch the video on the StewMac page.