An open source application for handling exceptions?

Is there an open source alternative for Hoptoad and Exceptioneer ? We would like to place an "aggregation" exception on our site.

Every day we receive dozens of .NET exceptions from users in the field. As such, we need a way to organize them, find duplicates, and prioritize the most common exceptions that occur. Hoptoad is nice and easy to use, but based on our initial tests, it didn't handle similar exceptions very well and doesn't seem to support storing / displaying all the information it needs.

I am looking for a tool that can be extended to our needs and deployed to our servers. Any advice?