If you don't mind delrin handles, then Schrade has a nice selection of slipjoints. Their Old Timer line is 1095 carbon steel and the Uncle Henry line is, I think, 440A. Both lines are good, solidly built knives, and take and hold good edges.
Bucks slipjoint line doesn't have as many models to offer, but they are great knives. Their construction is unique in that they use nickle silver liners that are one piece with the bolsters, and all the blades of theirs fold in straight, no bending like most other's knives have to do. They use 420HC, hollow ground blades. Take and hold a great edge, although it is harder to sharpen than Schrades steels.
Camillus slipjoints are good too, although all my Camilluses are older, discontinued models. Solid construction, and lots of history behind the company.
Case tru-sharp doesn't seem to be very good. Very attractive looking, but not very usable, according to most who have reviewed it. I have a Case Copperlock with tru-sharp, but I don't use it very often. I do have it really sharp, but I just don't know how well it holds an edge. Their CV is pretty good, I have two with it and I really like it. Case has an annoying habit of super polishing their blades, which means there are no squared edges, and the tips are always rounded. Very irritating.
If you look around, many of the German models (Boker, German Eye, Buck Creek, Bulldog...) are great knives. Queens are supposed to be the best quality American line, and AG Russels catalog has several excellent quality slipjoints, although the prices are a little higher.
If you don't mind used, check out E-bay and antique stores. I have good luck with both, especially with antique stores.
Hope this helped. I'm not an expert, I just like slipjoints. I'm hoping to add some of the ones I mentiond but don't have yet to my collection in the next few years, as time and money allow.
