Delicious: a social bookmarking site - I like it as a great resource not only for having your bookmarks available from any 'net access, but also for getting links to other sites that are relative to your interests.
Twitter: social updates, 140 characters at a time - Although I have an account, I rarely post updates. But it's a great place to keep up with celebrities, friends, and even better, deals.
Boing Boing: neat stuff on the 'net, consolidated - I subscribe to their blog for a peek into the bizarre.
Google: The search giant, that's branched into email, calendar, calculator, office applications and more.
YouTube: video sharing site - I uploaded my first video last week, and have found hundreds of great videos to watch and share.
Hulu: tv on the internet - I was able to give up cable for the sake of Hulu.
Amazon: online superstore - I'm a little aggravated with Amazon for cutting their ties with Rhode Island businesses in response to the R.I. internet purchasing tax, but you can find anything on Amazon, and I often do.
Netflix: online movie rentals - First there was Netflix, an inexpensive way to have a constant flow of DVD movies to your home. Then there was Blockbuster online, which offered the same service at the same price, and allowed you to trade in your online rentals for in-store rentals. Heaven! When Blockbuster jacked up their prices and severely limited service, I discontinued my subscription. Now Netflix offers video streaming as well as online rentals. It's a good service now. When they have more, newer movies available for streaming, it will be hard to beat.
Etsy: the Amazon of crafters - I love the finds on the different shops.
Wikipedia: online community-edited encyclopedia - It's not the be-all, end-all, but it's a great first source for information on just about anything.
Internet Archive: shots of websites from long ago - I've used this site to check out shots of my own sites to find missing content.
Facebook: social networking site - I like it for keeping in touch with family and friends.
Mint: financial management - links all your accounts together, helps with budgeting and tracking expenses.