Currently I am going to some lengths to better focus on only what is important at this very moment, and came across a very useful little freeware application: Spirited Away. Connected as we all are, a stream of email messages, IMs, tweets, and news is coming in, constantly asking for attention. We have even adapted to this with short attention spans and constant switching from one channel to the next. Spirited Away helps focusing on just the current task by automatically hiding all applications that have not been active in the last 60 seconds (adjustable, of course). I always liked the calming one application modus operandi of the iPad, Spirited Away brings it to the Mac.
If you also like a good read on the subject, I recommend the free ebook ‘Focus‘ by Leo Babauta. A premium version with additional chapters and videos is available, too.