Here's a quick video I put together to show you what Tarpipe does. If a picture is worth 1000 words, a video must be worth millions. This example shows an email being sent out with an image attached to the email. The email produces a new picture posted to Flickr, and the link for the picture is then posted to Twitter.
The purpose of Tarpipe is similar to Yahoo Pipes. It takes a source of data and posts it to a location. The sources available right now are of two types, email or a REST API. If you don't know what a REST API is, don't worry its not very important yet. But it means that it could read information from other websites. The destinations in the other hand are greater in numbers and some of them include WordPress, Twitter, Plurk, Facebook, Evernote and many others.
Essentially, Tarpipe allows you to send an email to a special email address, and this action of sending an email can trigger a whole process which ends up posting the body of your email to your Blog, and then announce it on Twitter while saving it to Delicious at the same time... for example. Anyway, check out the video and let me know if you have any questions. I also have a second video ready which improves on this one and should be made available later on this weekend.
The follow up video is now published, you can watch it here.