What is it?: Posterous is a great resource for those that want to have a web presence to upload information to share with the world without the hassle of running a full blown site or being worried about web programming or anything complex. As a teacher if you just want a simple web presence you can send your students and parents to for quick and simple information then this is ideal.
Essentially this is how Posterous works - Got a useful document, song saved as an MP3 or even a web link you want to share with anyone. Simply email it to email@example.com and it will be uploaded to your posterous web space. for example. www.yourname.posterous.com. Any file type can be uploaded to Posterous. It takes all of 2 minutes to register but you can even skip this step if you are keen.
How Can I use this in the classroom?: Post your weekly homework tasks up here. If you have made a podcast simply email it Posterous and it will play straight from the browser or you can download it. If you have a blog of your own you can automatically get your feed added to your posterous space. Anyhow Posterous is really worth a look and I am sure you can find a purpose or it in your own classroom.