using the overall top artists list on last.fm, divide into two sections the bands you've seen live and ones you haven't.
Artists i've seen live:
Animal Collective, Deerhunter, MBV, SY, Les Savy Fav, Liars, Yo La Tengo, M83, No Age, QOTSA, Jesus and Mary Chain, Shellac, Times New Viking, High Places, Aphex Twin, The Cribs, LCD Soundsystem, Mono, Jeffrey Lewis, Why?, Interpol, The Horrors, Crystal Castles, Women, Lightning Bolt, Black Lips, Justice, HEALTH = 28 out of 50
Artists still touring (who i can possibly see e.g. not dead) who i have yet to see:
Radiohead, Pixies, Mogwai (will be amended on Saturday), Throwing Muses, Weezer, EITS, of Montreal, The Magnetic Fields, Portishead, Wu-Tang Clan, Echo & the Bunnymen, Flying Lotus = 12
12 more to go, i reckon, with those bands, that might take me 4 years to do, barring any personal financial meltdowns.