I bought (a few years ago) a Singer online for $99 and use it on my quilting frame. It is a fantastic machine and works great. I am hoping to get a mid arm one of these days, but for now, the Singer can't be beat!
Before I had this one, I used my old Singer for free motion quilting when I didn't have the Handiquilter frame I have now. I was new to FMQ and just did squiggles and stuff but it did fine. My new machine now is a Brother and is computerized which I didn't really want, but seemed to be all I could find. It is a great machine too, and I use it to quilt small things like table runners.