Somewhat unexpectedly, there's been a lot of interest in doing work related to Semantic MediaWiki for the Wikimedia Foundation's part in this year's Google Summer of Code. Here's a student who wants to create a natural-language querying interface for SMW, possibly by improving the "Ask The Wiki" extension:
And here's another student's idea, that was actually brought up on this mailing list, to improve SMW's importing of RDF:
And then there's the third item on this list:
...Jeroen's suggestion for adding more GIS-type functionality to Semantic Maps.
I unfortunately can't mentor any of these, because I have my own proposed project (the second item on that list :) ). But there may be others who can. If you've done any SMW-related (or even just MediaWiki-related) development, and find any of these projects interesting, please consider signing up as a mentor, and/or contacting that student directly (for the GIS one, send an email to Jeroen). From personal experience, I can say that being a GSoC mentor is a very rewarding experience - you get to see a project come to life, without having to take care of all the little details. I would definitely recommend it.