This list started with the Wired article 100 Geeks You Should Be Following On Twitter" -- feel free to add and expand!

Name Twitter ID Geek Cred
Dtoombs DtoombsMC Minecraft Player and Youtuber
OverClocked Remix ocremix A community dedicated to the appreciation, preservation, and interpretation of video game music.
Yankovic, Weird Al alyankovic Geek music icon.
Plait, Phil badastronomer Well-known astronomy blogger.
Doctorow, Cory doctorow Science fiction author and founding member of Boing Boing.
Pettis, Bre bre Maker extraordinaire.
Sagal, Peter petersagal Host of Wait Wait, Don’t Tell Me.
Duane, Diane dduane Celebrated science fiction author, especially famous for numerous Star Trek novels.
Savage, Adam donttrythis Co-host of Mythbusters.
Norton, Patrick patricknorton Tech journalist, host of Techzilla podast.
Call, Marian mariancall Gifted musician and all-around geek.
Hodgman, John hodgman Writer, performer, geek humorist.
Scalzi, John scalzi Veteran blogger; science fiction author; Stargate: Universe creative consultant; Bacon Cat creator
Gaiman, Neil neilhimself Author of “Sandman”, “American Gods”, “Coraline” etc.
Hardwick, Chris nerdist Comedian, actor, writer
Massimino, Mike Astro_mike NASA astronaut, mission specialist for STS-125 (launches on May 12, 2009)
Knowles, Harry headgeek666 Founder of AICN, Movie reviews of the geek variety (SciFi, Fantasy, Horror and Comics)
Coulton, Jonathan jonathancoulton Musician, Writer and Singer of songs with geek themes (ie the Portal song).
Gibson, William greatdismal SciFi writer and one of the Pioneers of Cyberpunk Fiction
Lady Ada adafruit Hacker and Open Source Hardware advocate
Torrone, Phil ptorrone Senior Editor of Make Magazine
Wozniak, Steve stevewoz Inventor of the Apple Computer … nuff said
Wyatt, James aquelajames Wizard of the Coast, author of 4th edition DMG
Mearls, Mike mikemearls Lead developer of D&D R&D at WotC
MC Frontalot mc_frontalot Nerdcore rap extraordinaire
Ellis, Warren warrenellis Comic book author and curator of the weird
Hryb, Larry majornelson Aka Major Nelson; Director of Programming for Xbox Live
Paul and Storm paulandstorm Awesome geek musicians
Day, Felicia feliciaday Star of “The Guild” and “Dr. Horrible”; she not only plays geeks but is one
“Gabe” Krahulik, Mike cwgabriel Artist behind Penny Arcade
“Tycho” Holkins, Jerry tychobrahe Writer behind Penny Arcade
Imahara, Grant grantimahara Associate MythBuster
Smith, Kevin thatkevinsmith Movie director & actor; serious comic book and movie geek
Kovalic, John muskrat_john Awesome cartoonist and writer of Dork Tower
Favreau, Jon jon_favreau Director of Iron Man
Burton, Bonnie bonniegrrl Editor/writer at Lucasfilm, cutting edge geek
Fry, Stephen stephenfry British comedian/fop/mac head - loves his gadgets, writes for Guardian
Bradbury, Jason JasonBradbury Presents ‘The Gadget Show’ in the UK, tweets incessantly, ‘Dot Robot’ author, father, rides a Sinclair C5
Gorman, Dave davegorman Comedian and star of such shows as ‘Dave Gorman’s Googlewhack Adventure’ and ‘Are You Dave Gorman?’ Lover of Powerpoint and spreadsheets.
Burton, LeVar levarburton You know, from Star Trek. Plus loves books, kids, etc.
Anderson, Chris chr1sa He founded GeekDad.
Izarik, Justine ijustine Life-streaming pioneer and new media darling, her YouTube videos are hiliarious and geeky.
Bwana bwana Gamer, podcaster, and tech blogger. Plus, he does a mean Patrick Norton impression.
Templesmith, Ben templesmith Gifted comic book artist. Draws great zombies, and the best Dr. Who ever.
Frauenfelder, Mark frauenfelder Editor in Chief of Make magazine, and founder of Boing Boing.
Belmont, Veronica veronica Tech journalist, co-host of Techzilla.
Trapani, Gina ginatrapani Founder of Lifehacker.
Koford, Adam apelad Comics artist, creator of the LOLCats strip.
Doctor Popular docpop Gamer, yo-yo artist, and denim-repurposer.
Johnny Johnny tikijohnny Bartender for Tiki Bar TV, and cartoon maker.
Macpherson, Jeff drtiki Doctor Tiki from Tiki Bar TV.
Ihnatko, Andy ihnatko Tech journalist and major geek.
Gruber, John gruber Technology reconteur and font geek.
Jardin, Xeni xenijardin Writer for Boing Boing, and host of BBtv.
MacArthur, Amber ambermacarthur Tech journalist and video blogger.
Cleese, John johncleese Monty Python alum and gadget geek.
Kawasaki, Guy guykawasaki Tech journalist.
Rose, Kevin kevinrose Founder of Digg.
Williams, Evan ev Founder of Twitter.
Bettany, Lisa mostlylisa Photographer and blogger.
Lane, Sarah sarahlane Tech journalist and video blogger.
Amend, Bill billamend Geeky cartoonist (writes the FoxTrot strip)
Laporte, Leo LeoLaporte Technology journalist
Dash, Anil anildash Long-time blogger; 1st employee of SixApart
Penagos, Ryan Agent_M Inside-scoop blogger at Marvel Comics
O’Reilly, Tim TimOReilly Founder of O’Reilly Publishing, Web 2.0 conference
Camp, Garrett gmc Founder of StumbleUpon
Grunberg, Greg greggrunberg Actor on Heroes and serious web geek
Lore loresjoberg Writes for Wired, seriously strange (but very funny) guy
Jillette, Penn pennjillette The speaking half of Penn & Teller; mostly a magic geek
Beale, Scott laughingsquid Founder of the geeky blog Laughing Squid
Tyson, Neil neiltyson Astrophysicist, author of several astronomy books
Kinsman, Berin unclebear Father figure of the RPG bloggers. Has been blogging about RPG’s for about 13 years and there isn’t anything he doesn’t know about the subject.
Kurtz, Scott pvponline Webcomic artist/writer behind Player vs. Player
CAG videogamedeals Deals update feed from videogame shopping site Cheap Ass Gamer
MC Lars mc_lars Post-punk laptop rapper
Wizrocklopedia wizrocklopedia Your Wizard Rock news source
Nerdapalooza Nerdapalooza Orlando’s own large-scale nerd music festival
Ruybalid, Anthony genoboost Of chiptune/VGM site Game Music 4 All
Waldman, Ariel spacehack a directory of ways to participate in space exploration, interact + connect with the space community and encourage citizen science.
Benson, Amber amber_benson Buffy actor and comic book geek.
Lewis, Cali calilewis Tech maven, video blogger.
Pirillo, Chris chrispirillo Tech journalist, life streamer.
Reznor, Trent trent_reznor Creative force behind Nine Inch Nails, tech geek, music geek, and a driving force in changing the music industry.
Pogue, David pogue Tech writer for the NYT.
Bendis, Brian Michael brianmbendis Comic book writer.
Geek Girl Diva geekgirldiva Geeky blogger and affiliates manager for Entertainment Earth - lots of cool toys!
Peters, Jayson nerdvana Geek blogger.
Lunde, Alison snipeyhead Code monkey and sarcastageek.
Boyer, Brandon brandonnn Editor of Offworld.
ThinkGeek thinkgeek Twitter feed from the geekiest store online, manned by various staff, and always interesting.
Pixelh8 pixelh8 Renowned chip tune musician and music software designer
Cuban, Mark mcuban Dallas Mavericks owner, founder of HDNet, Media/Tech blogger
McGonigal, Jane avantgame Game designer & researcher, alternate reality gaming (worked on the “I Love Bees” Halo 2 project)
Newitz, Annalee Annaleen io9 editor/writer; science/tech journalist
Hutchinson, Grant Splorp Font nerd, also quite possibly the foremost Apple Newton expert. Runs a web server on a Newton.
Harris, Kaden kaden_harris Eccentric Canadian tinkerer and O’Reilly author.
Gurstelle, William wmgurst Author of numerous catapult and ballistics books, MAKE contributor and MAKE:Television producer.
Oskay, Windell oskay MAKE contributor, tinkerer
Phillips, Eliot sweetums Editor of Hack A Day.
Burns, Laura moonrangerlaura Space News