I actually don't have any good advice on this one. I can tell you that going to a SQL Saturday, or better still, the Summit, has a tendency to get me re-energized about my work. I guess it's that reinforcement that even though you're doing it alone, you've got sympathetic ears, so it doesn't feel quite so lonely. That, and you hear stuff that gives you ideas and gets you going. But that is a tough question.

Barring Summits & other huge events... try learning something different. Instead of pounding your head on the same old technology, check out PowerShell or SSRS, SSAS, nHibernate (maybe skip the last one). Getting some passion in one area frequently translates into others, same way as being really down in one area drags down others.