Viator - tours, activities and things to do on vacation

What they say:

"Viator is the leading online provider of destination travel products: sightseeing tours, theater tickets, attraction passes, theme parks, even zero gravity flights...the things you do when you get there. Our market-leading selection of products includes 4,000+ tours and attractions, in over 400 destinations located in 65+ countries worldwide.

A sampling of our product offering:
Whale Watching
Helicopter Tours
Classes
City and Rail Tours
Cycling & Hiking Tours
Airport Transfers
Dinner Shows/Opera/Plays/Theater
Shopping Excursions
Safaris"