If you ever looked at ikiwiki but gave it a pass since plugins had to be written in perl, you might want to look at it again now. Today I added support to ikiwiki for plugins written in any language that supports XML RPC. Ikiwiki's external plugins are just standalone executables, that talk XML RPC on stdio.
I think that works pretty well. The overhead of XML RPC doesn't matter too much in this case, since RPCs arn't done all that often. The entire ikiwiki programming interface is accessible, except for a couple functions that use perl objects. I even added the ability to inject an arbitrary procedure from the external plugin into perl, so ikiwiki can call it like a regular perl function. This can even be used to override one of ikiwiki's functions with a version written in another language. Even parts of ikiwiki that don't use a defined plugin interface, like the RCS modules, can be written in other languages using this.
Now I only have to find time to learn enough haskall so I can write ikiwiki plugins using it. :-)