I've found Offgamers to be the best. Just highlight "powerleveling" on the bar at the top and then click "show games"

I like them for a number of reasons. First off, they have gotten a lot of positive reviews from other users. They do a fast job and are very professional. They level the characters by hand, no illegal 3rd party software is used. This greatly reduces your chances of getting banned.

They have plenty of options including if you want professions leveled or you want some extra gold. They also offer something I really like, insurance! If you are worried about getting banned, they offer an insurance option. Should you get banned, they'll buy you another account (including expansion if you had it) and level you a new character! Now that's some good security.

There are several things to keep in mind when using a powerleveling service.

1)Use a new account if you can. That way if something goes wrong, your characters are safe.

2)Your account could be banned. Getting the insurance helps reduce this. Some powerleveling services use bots to level their characters. This is EXTREMELY risky and may lead to your account being banned several months down the road (as Blizzard tends to ban botters in "waves").

3)Don't log into your account during the leveling process. Number one, it could effect the powerlevelers from being able to access your account. Number two, and more importantly, having multiple IPs hit an account at once gets it immediately flagged. From there a ban is almost enevitable.

4)Whatever service you choose to use, do your research. Some are legit, some are scams. Generally, ones you haven't heard of perform better. Popular ones (like IGE) tend to have bans left and right because Blizzard knows all about them.