Solution: Smaller solution. Seriously. Just create a new solution that has just the projects you need. That's what I do when I get solutions with more than 50 or so projects in it. I'll create a new Solution with just the 4 or 5 that I really need. That way I'm not having to rebuild the entire Empire State Building when I remodel an office. Also, if you use the Build option (Ctlr+Shift+B) it should only be building projects that actually changed, and skip over any that didn't.

-tg