Can I give away Steam games?

Pay attention that selling the account is not allowed by Steam Subscriber Agreement.

When you complete Steam's registration process, you create a Steam account ("Account"). Your Account may also include billing information you provide to us for the purchase of Subscriptions. You are solely responsible for all activity on your Account and for the security of your computer system. You may not reveal, share or otherwise allow others to use your password or Account. You agree that you are personally responsible for the use of your password and Account and for all of the communication and activity on Steam that results from use of your login name and password. You may not sell or charge others for the right to use your Account, or otherwise transfer your Account.

The only way to send games to friends is in the checkout option, selecting Purchase as a Gift

Relevant section from the link above:

Can I gift games I no longer play to my friends?

You can not gift games that were previously purchased on your Steam account to friends.

Once you purchased it for your account, they are not transferable.

A lot of people are speaking to the legality of the issue, which is important. However, as far as practicality goes, yes, you can sell/give your account information to a friend.

This is against their terms of service, and I'm not advising it, but technically you can't sell your WOW account either, and that's common practice. As Drake pointed out though, you do have billing account info associated with that account, and if you don't change it or deactivate it, your 'friend' might start buying games and you'll have to pay for them.