Can you tell if your friends are playing without going all the way in-game?

I'm new to World of Warcraft and I'm only really interested in playing when certain friends are online. Is it possible to view the status of friends in your friends list without launching WoW and fully entering the game?

To my knowledge Blizzard has not yet provided a way to view friend status from outside of their games. So you'll have to go with a 3rd party solution.

I use Steam to launch World of Warcraft. Steam will notify my friends when I launch a game, and vice-versa. Most of my friends also use Steam, which increases the value of Steam tremendously. There's little quite as satisfying as launching WoW and then seeing 4 more of your friends follow your lead. One downside to Steam is you have to own at least 1 game on the service to get the friend features.

Also, steam doesn't tell you what character they're on, but once you're in the game RealId can help figure that out really quickly. If you don't use RealId with these friends, there are a number of friend-synching addons you can use to keep track of friends across multiple characters on the same server/faction.

There are also a few alternatives to Steam (XFire?) for keeping track of what your friends are playing. A common thread across all of these is that all your friends will want to use the same program.

I know this is an old question, but Blizzard recently added the Mobile Guild Chat feature to the Mobile Armory. For a small premium fee, you can sign in to the guild chat and see which of your guild members are online, as well as chat with them. Assuming your friends are in the same guild as you, this is the best option by far.