All kinds of options... be sure to search for drum machine / drum software.
Personally, I picked up a zoom RT-223 ($100 used). It has lots of sounds, and can store up to 50 drum kits and 500 patterns.
http://www.zoom.co.jp/english/products/rt223/index.php
I like that I can use the RT-223 as a practice amp, by just plugging in my bass, and firing up a few patterns and playing along.
The Alesis SR-16 is very popular as well. I don't have any experience with it, but it's been around a LONG time, and is considered to be very good (even after all these years).
Those are both drum machines... It's easier to use software, but you can't always have a computer near by to fire up the programs.
One popular/free program is Hydrogen...
http://www.hydrogen-music.org/
Both software and drum machines will require a learning curve (unless you use pre-set patterns)... but it's easy enough to overcome if you have some music knowledge (which you probably do).