Exim4U is a Web-based user interface and integrated software configuration for the Exim message transfer agent (MTA). Using any modern Web browser, you can use it to manage Exim email domains, user accounts, aliases, forwarders, and much more. Exim4U is a derivative work of the Virtual Exim (Vexim) project.
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solardiz and imipak make good points as well. though i dont see there being a single perfect option. So whilst i still think that hooking in to project hosting sites is a really good option, i 100% support the idea of making non-maintainer updates easier. In terms of point 1, it may be worth publishing an API so that sites like sf, github, alioth, or new upstarts can feed in updates easily. There could also be something like the 'open graph' protocol which project owners can embed in their sites HTML, allowing freecode to suck out the latest versions, or maybe just a yaml metadata file... http://someproject.org/freecodemeta.yml for example. For point 2, perhaps create some sort of facebook-ish 'like' button that projects can put on their sites. This would be very social indeed.
Again, i dont think this is a silver bullet and fully support any other great ideas people may come up with as well.