Processing post content before it goes into DB
 

I would like to get a shot at processing the content of a post before it goes into the database. Where can I plug in to do this? Any mods or articles that I can look at for guidance and inspiration?

I want to primarily be able to create functions that can filter message content according to our rules. This could go from validating links to just about anything else one can imagine.

No, I can't use the built-in bad language filtering facility as it is too limited in functionality and smarts.

Thanks,

-Martin