Just wondering if there are any controllers that can be used for games like Redneck Rampage or Postal. I suck at using the keyboard and mouse and (even though it's almost a sin in the eyes of many PC gamers) preferr a regualr controller for gaming.

I know the 360 controller can be used for some windows based games, but what, if any are pretty good, cheap controllers for the PC?

Actually, as far as gamepads go, the 360 controller is pretty much the best. Just grab the wired version. I swear by mine. Think they retail for $20-$30. WELL worth the 20-30 bucks. Very solidly made, great driver support (no idea why :p), and actually pretty comfortable.
Plus, if you ever try to emulate the console games you legally own, the 360 gamepad will work for just about anything short of the N64 controller (and maybe Dreamcast).

To use it with games that don't support it: download XPadder (think it is pay now, but there used to be a free version), which lets you basically map the mouse/keyboard to a gamepad/joystick.

If you already have an XBox or PS2 controller lying around, usb adapters for them are a dime-a-dozen (well, literally $2-$5) on eBay. Gamecube ones tend to be a bit more expensive and less common due to less demand. PS2 adapters tend to be twin adapters for one or two controllers in one port. XBox usb adapters are sometimes more expensive due to the higher demand caused by their usefulness in modding the consoles, but it's usually not hard to find a good price.

JoyToKey is my favorite program for mapping keyboard and mouse commands to controllers. (An interesting story, it was my tool of choice for playing Google Pac-man a few months back, with a custom arcade stick no less. Yeah, that's the way Google Pac-man was made to be played. XD)

Just be sure you disable joystick in the game you're running or in DOSBox itself to avoid conflicts. Again, adapters for PS2 controllers are the cheapest and easiest to find. I made my arcade stick from a modified PS2 controller for this reason, and have PS2 to XBox, Gamecube, and USB, making it a universal controller for PC, XBox, PS2, PS1, Gamecube, Wii, and from what I've heard, USB controllers will even work on a PS3. It's great if you like to play on different systems and want to use your favorite controller. Good stuff.