Top Deck Tours
Top Deck is much like Contiki and you can see their website at:
They also offer 3 different types of travel options, Hotels, Cabins, Camping, but with Top Deck it's not as organized and rigid as Contiki.
You have more freedom to choose what you want to do but I also found you didn't get as close to the people as you did on Contiki.
Top Deck offers many fewer travel destinations but I found the trips I went on were to more exotic destinations, like Russia.
Also the thing I liked about Top Deck is they throw in lunches in the price of your trip which Contiki do not. Top Deck is also A LOT cheaper then Contiki in most instances.
If you were taking your first trip, I'd say go with Contiki no doubt, because your money will be well spent, but if you want more freedom of choice and your on a tighter budget, go with Top Deck.