If you've ever been at a loss to describe something to someone on the phone or over IM, free webapp Woobius Eye is the answer—with a simple link, your conversation can turn into a visual discussion as easy as doodling.
At first glance, one may wonder why they would possibly need another doodling app—up until now, so many just seem gimmicky. But the addition of another party to the app all of a sudden affords infinite possibilities—things that were too difficult to describe over the phone or over IM are instantly simplified. You can upload images from your computer or snap them from the web, then draw on them to make your point (and then your friend can agree, or shoot your idea down by drawing theirs instead).
Inviting someone to the app is a cinch, too—all you need to do is open up the page yourself, hit "invite", and you get a private link that you can send over IM. Check out the video above for just a few of the practical possibilities (and they've outlined a few more on their blog). In addition, they are working on a mobile version so you can visual chat on the go.
Woobius Eye is a free web service, no sign-up required.