Database shared across more htan 1 domain

Hi
We use wordpress for our main web site and want to be able to use sections of it (different categories) to provide content for a couple of other small specialist web sites – i.e. for them to effectively act as a mirror with a bit of code adjustment so they only include the categories relevant for each mirror site. My question is whether its possible for wordpress to be configured to access the database of a different URL? The sites are on the same server, but with different domain names, and the wordpress content woudl only ever be updated on the main site. I’m guessing this may be acheived be giving wp-config the correct MSQLhostname (but I’ve tried several to no avail) or somehow configuing our Linux virtual private server (running plesk) to share the database? Can anyone offer any guidance on how to do this? Assuming its possible is there also a way to provide a simple re-direct on the mirror sites so that when they include an image in a post they go to the main site image folder instead of their local folder?

Many thanks
Adam