with antivirus/antispyware powered by ClamAV (it will have an option of scanning incoming webpages from all the mainstream web browsers for viruses or malicious code as well as phishing filter), an optional web filter for schools or parents who would like to filter their kids searching, and possibly some other things. This should be really fun. One disappointment I found is that the ClamAV bindings for C# haven't been updated since October of 2005 :-/. So, I will probably write my own.
I haven't decided on a name yet, but that isn't the most important thing right now.
Another thing I might start is the GIT# implementation needed for MonoDevelop.