On Flickr there's a useful thread describing a quick trick to make colours pop. You take your photo, convert to Lab color mode, then compress the a and b colour channels. This has the effect of making colours generally brighter at the cost of destroying some detail in intensely coloured parts of an image.
Not always a good idea, but it can make certain pictures look better. I've done it to about 5% of my photos I put on Flickr. To make life easier I've created a Lab color pop action set for you to download. First you should try the method manually once to understand what it's doing.