Gavin Andresen- Profile the project maintainer. He previously worked at Silicon Graphics and now runs his own company.
Mark Karpeles- Known as MagicalTux on bitcoin forum and in the #mtgox channel in freenode IRC network. Owner of the largest bitcoin exchange, MtGox, and Kalyhost
Vladimir Marchenko- Profile, runs Marchenko Ltd which sells mining contracts, previously developed the figator.org search engine.
Jeff Garzik- Wikipedia Entry who does kernel development at Red Hat and is the founder of BitcoinWatch.
Matt Corallo- uses the moniker of BlueMatt on bitcoin forums and other sites, Is a core developer of bitcoin.
Pieter Wuille- uses the moniker sipa, is a core developer and maintainer of the network graphs http://bitcoin.sipa.be
Stefan Thomas- uses the moniker justmoon, creator of the WeUseCoins.com site/video and WebCoin.
Hal Finney- Hal, one of the creators of PGP and one of the earliest contributors to the bitcoin project.
Michael Hendrix- uses the moniker mndrix, creator of the now defunct CoinPal and CoinCard services
Michael Marquardt- uses the moniker theymos, creator of the widely used blockexplorer.com site
Amir Taaki- uses the moniker genjix, creator of the Britcoin exchange
Mike Hearn Profile- Google engineer who works on Gmail and developed BitCoinJ (http://code.google.com/p/bitcoinj/)