Dillion makes some pretty decent knock-offs. My buddy had one of their PRS copies a while back, and that was actually a really great playing and sounding guitar. I was looking for one for a while too, but ended up getting a PRS SE instead.
As for Stingray knockoffs, I've had two OLP's and three SBMM. The OLP MM3 (5-string) was my first 5 string, and actually played really well. The electronics left much to be desired, however, but for being one of my first basses, I didn't mind. I gave that away for free to a budding bassist. I also had an MM2 (4 string). The previous owner installed a Seymour Duncan Basslines pickup, and it sounded decent. This one didn't play nearly as well as the MM3 though, and it was around this time I realized I didn't want knockoffs anymore (had knockoff P's and a Dean Warwick-thumb copy, wasn't happy with any of them). After that I got into the Sterling by Musicman (not really a knockoff), which are great basses and I like them a lot, but in the end, I just like the real deal too much, and I'm currently on my second Stingray.
There are obviously some high quality clones available with P's and J's and various others, but they aren't always easy to find. Sadly, it seems like there are far less choices when it comes to stingrays, and even fewer decent models.