Sure.... I basically monitor my PPC spending/activity like the stock market. Seems like I get a lot more qualified click-throughs and results on Fri-Sunday... especially sunday. So I vary my spending by day and really increase it on the weekends. But it all depends on your audience and their usage. I now split my spending to 50% US and 50% international. I'm also getting into geo-targeting and content match.
I'm also changing bids on specific terms and keyphrases constantly and also bidding based on current events, holidays, etc.
It can be a time consuming process to do it properly but anymore I pretty much have a set system that is easy to manage.