Petition to Google to Open Source Google Reader
Please type +1 and your name in the comments. If you work at Google then please talk tell your management to look here.
The interesting bit is the 'backend', the crawler and database, ie the servers that supplies the API. But that simply can't be open-sourced, as it too Google centric.
I just used TT-RSS for the backend, and built my own GReader like front end in a matter of ours.