I've just returned from an expedition to the Ross Sea aboard the 'Kapitan Khlebnikov' with Quark Expeditions. Definitely the trip of a lifetime - the scenery, wildlife, historic huts etc are just awesome and we also visited several science stations. I can't recommend Quark too highly; their logistics are superb (ship, helicopters, zodiacs) and the expedition staff are fantastic!
If you can afford it (and it's not cheap), then a voyage on an icebreaker rather than just an ice-strengthened ship is the way to get to the places others can't, and the helicopters do add a whole extra dimension to the possible range of shore landings (plus sight-seeing flights as well).
The Lonely Planet 'Antarctica' guide has good info for trip planning, and a google search on 'antarctic tourism' will also point you to several useful sites.
Finally, take far more film / video tape etc than you think you could possibly need...! :grin: