When I edit my web project references, I can't find the System.Web.MVC2 assembly in the GAC.
That's not what I expected since the Synaptic Package Manager reports that libmono-system-web-mvc2.0-cil package is installed properly.
When I edit my web project references, I can't find the System.Web.MVC2 assembly in the GAC.
That's not what I expected since the Synaptic Package Manager reports that libmono-system-web-mvc2.0-cil package is installed properly.
Try installing it to the GAC manually.
Not all assemblies need to be in the GAC. There may be a reason the ASP.NET MVC assembly is not installed in the GAC (ease of deployment?)
Assemblies in MonoDevelop's Edit References list are not taken from the GAC. This is also true of VS and .NET. The GAC is only meant to be used at runtime, not compile time.
When targeting Mono, MonoDevelop uses a system called "pkgconfig" for discovering assemblies. When targeting .NET, it uses the same "Assembly Folders" keys in the registry that VS does.
Note that in MD Preferences you can also add additional folders to be searched for pkgconfig files or assemblies - this is intended as an easier alternative to properly installing them onto the system.
Since you use Ubuntu, which breaks Mono into many tiny packages, it's possible that Mono's pkgconfig file for the assembly has been split off into a separate -dev package, so you might try looking for that (though I'm not sure whether 2.6.7 included the pkgconfig file - maybe you'd need 2.8).
Also, MonoDevelop 2.6 does not yet exist - you probably mean 2.4.