My current favorite source is
http://www.adultclothdiaper.com/. Great quality, fair prices.
They have many types, including pull-up, velcro, pre-fold and fitted (in different materials and thicknesses), plus stuffers and AIO (all-in-one) styles. Since you are new to cloth, I'll translate
*pull-up: like a big baggy pair of tightey-whiteys, only thicker. Not a very precise fit, but easy to put on- somewhat unnatural shape and potentially obvious.
*velcro: hourglass shaped, like a disposable baby diaper, held in place with velcro strips. Better fit than pull-ups, still easy to put on. Pretty form-fitting, not particularly obvious.
*prefold: the common rectangular standard, as used by cloth baby diaper services. These are rectangular (longer than wide, and typically much thicker in the center third (lengthwise, front to back). They are called "pre-fold" because before this type existed, you would fold a single sheet of fabric into a diaper, layering it thickest in the middle. By sewing the layers in place, the "pre-fold diaper" took a lot of work out of putting a diaper on. Ironically (especially since the "prefold" comes sewn together, not than folded), you need to fold a prefold to make it fit really well (how best to do this is an entirely different discussion). Best overall fit (if folded and pinned expertly), best leakage protection, arguably most "baby-ish". Very unnatural shape, potentially very obvious. Requires use of diaper pins.
*fitted: diaper cut in an hourglass shape. Velcro diapers are typically fitted, and you can also get them without velcro, designed for use with diaper pins.
*stuffers: extra layers, basically the center part of the diaper, without the wings. You place one/some inside/in-between regular diapers to increase bulk of your diaper- for increased absorption capacity, or just because you like thick diapers!
*AIO: "all-in-one" diapers. Basically a pull-up or fitted diaper with a waterproof outer layer- absorbent diaper and plastic pants all in one . . .
Speaking of which, don't forget the plastic pants!
Another great source is
http://www.babykins.com/adult-incontinence-products/.
I've read good things about
http://www.fetware.com/ &
http://www.baby-pants.com/diapers.php as well.
Cheers, enjoy your new cloth diapers!