I would like to be able to search on the StackExchange gateway for a subject and get a list of the most relevant sites (possibly Google instant style, filtering the normal list). Searching is often a lot faster than scrolling through a list, and this one is growing all of the time. If there are several similar sites it could also help seeing the difference without reading through several FAQs first. This could be a good answer to "where should I post this question?".
The search should probably be based more on the tags and the site FAQ/description then on the actual questions.