Twitter recently acquired Posterous and there has been some talk about it shutting down. Naturally some people would like to get their content out of the system sharp-ish but the latest API needs a key.
I wrote PostLib ages ago when I was looking to process content from Posterous offline. I couldn't find the original project (but I had the debug version of the dll referenced in an old project). I've used Reflector to extract the source code and update it to .net 4.0 (it was 2.0). No promises on it's full capabilities or the quiality of code but it should help out someone. You can grab it from here
It uses the old API so it may not be perfect, but it does seem to be responding with the expected content. Hopefully it'll help people out. You can use it by putting a reference to the project and then doing the following: