Kimberly Winston has a website , and has written a book about prayer beads in the various religions. Her blog has a great deal about Catholic beads, but presumably she's planning on talking about the use of beads in other world religions -- and it seems like virtually all of them have some sort of prayer/meditation practice that uses beads. But she's starting with Baha'i prayer beads.
Besides the requirement in the Aqdas to recite "Allah'u'abha" 95 times, prayer beads can be used for a variety of repetitive meditations, to suit the devotee. There's the "Remover of difficulties", which Baha'u'llah has been reported to have told the friends to recite 500 times, or even more. There's the Quran verse 65:2-3, which Alison talked about on her blog. For a while the verse from the Kitab-i-Ahd: "Say: All things are of God" was popular among the cyberspace community. I have also, at time, borrowed from Muslim or Christian practice.
I got my prayer beads from Special Ideas. They are blue sodalite, which is one of the minerals composing lapis lazuli. According to folks who believe in the mystical properties of semiprecious stones, sodalite is supposed to represent "truth" -- an idea which I rather like to be reminded of as I pick my beads up.
All that being said, I actually prefer meditation without using prayer beads -- a kind of centering prayer focusing on Baha'u'llah. But He has left us with a great deal of latitude in our devotional lives; there's lots of room for experimentation.