How to convert text content at runtime

Hi Guys,

I’m interested in created a plugin for my site to rewrite keywords, and add a link to them. My question is, how can I access the post content during the loop, parse the data, and then echo the revised content out. Kind of like how chitika will rewrite certain keywords. I’m just not sure where to begin with it. I know how to parse the data, where I’m getting lost is where to “hook” into without screwing something up, or having the original content and revised content posted together. Does this make sense? Any help in pointing me in the right direction would be appreciated.

Thanks