I think that a board navigation on the top or bottom of the page would help me get curious about boards I don't visit very often. I never use the navigation frame and I think most people don't either.

Also, it could help to feature good threads on the homepage - kind of like wakachan does with the image of the day for example. Basically something that shows actual activity.
Since there's a splashscreen and only a news post every 3 months, the homepage is kind of a missed opportunity.