Bounce Rate Demystified
blog.kissmetrics.com
blog.kissmetrics.com
If your pages contain good quality content and your traffic is coming from targeted (good quality) sources, your bounce rates will decrease. On average if you increase the content and quality traffic of your website, the bounce rates will naturally decrease.
For this reason, I've often thought that Google should rename Bounce Rate to something a little less erroneous involving the word "quality".
Also, It's worth adding (to me, at least) that a Flash site will have a skewed (higher) bounce rate because most/all of the content is in the .swf in a single .html page. We often have customer freak out over their 95% bounce rate.