While you can find plenty of follow focuses online, some are hefty but fairly expensive while others are of a less-than-desirable build quality and rarely have the filmmaker in mind when they are being designed. This Lanparte follow focus caught my attention not just because of build quality, but also the price -- for around $400 (depending on where you buy it), you can get this model with hard stops and a handy quick release system that makes attaching and removing simple. Below is a video review of the follow focus.
Below is a review thanks to Cheesycam from LJ Lee:
Video is no longer available: vimeo.com/42956578
While $400 is not a bargain basement price, I think for the design this actually does a great job competing with much higher priced items. It seems that this was designed to compete with the Arri MFF line of follow focuses, and even though those offer more features, they are 3-5 times the price of this one. If you're on a budget and you're looking to build a cine kit with your DSLR or Sony FS100 -- or even higher end camera -- this is a good option with hefty build quality, removable gears, a removable marking ring, and most of all, hard stops which are essential if you're using these with kit lenses or Nikon G or Canon L lenses which don't have built-in hard stops of their own.
You can find this device on eBay, or there are other various retailers selling them on the web. It doesn't seem like the Lanparte website is working at the moment, but you can certainly take a lot of information from the great review above. Links to buy the follow focus are below.