You can also add a helper coil... around here thsi has become known as "zuk coilds", due to a user "zuk" explaining the possibilities.
Basically, you get a coil spring, and squeeze it in between the upper and lower bump stops on the leaf spring, where they meet the axle.
The amount of lift you get wil ldepend on teh springs chosen.
the cheapest (often free) route is to find somebody w/ some leftover stock TJ springs, from their upgrade... this is teh kind of thing you can get for a 6-pack and/or as handshake. Just cut it to the length you want, sqeeze it in there, and you're done.