I don't use any. I find that organizing them by myself just as efficient, or not, as any manager. The fonts that your computer uses are in the windows/fonts folder but I made a separate folder, called fonts, on my drive and I keep all of mine there divided into subfolders like calligraphic, handwritten, techy, gothic, old west, grunge, dingbats, etc. Depending on your computer you can only have so many "loaded" into the windows/fonts folder at one time. Older pcs have around 1,500 max and newer pcs 3,000 plus (mine maxes at 3,500) but, if you're like me and have way more than that, you have to keep them somewhere else. What's more important is a good font viewer that can load from a directory other than windows/fonts. I'm using Main Type and Font Creator both from High Logic but I used to use a free one but I can't remember what it was called. The AMP free viewer looks very similar to what I'm using.