I found an Ansco Titan (yet another variation of the Isolette and Speedex) at an antique mall for $15. It had swiss cheese bellows and fungus in the lens, but felt pretty sturdy, and the shutter seemed to be firing okay. After cleaning it up and patching some holes with nail polish I ran a test roll through it. I was so impressed with the picture quality that I went out and found a nice, clean model (and it didn't cost a whole lot more). It's become my standard daytime camera when I don't want to carry much.
The Titan has a f/3.5 90mm anastigmat lens. It's labeled Ansco, but I've read gossip that claims that the lens and shutter were built by Wollensak. One of my favorite features is the color coordinated DOF scale. It takes the standard 12 6x6, and fits into my back pocket like a stuffed wallet.
After using the Titan for a while I found a clean Zeiss Ikonta 6x9 folder with a tessar lens (for quite a bit more money that the Titan). I really enjoyed using it also, but after doing some tests I found I really couldn't tell the difference between the lenses at up to 11"x size prints, so I went back to using the Titan. It's a little smaller, and I like square images anyway.