Link Building strategy between domains I own?

[KHCreative]

I am in the somewhat unique position of owning and administering around 300 websites that each have their own unique domain names.  We have a corporate website and then many individual websites for hospitals and nursing centers that we operate.  My question is how would you recommend using these sites to build good incoming links between all the sites?  Should I take every opportunity to find as many places to link from each site to all the other sites that are owned?  Is there anything I should avoid that Google would penalize me for or discount the links all together?  Sorry this is a such as long question... but wasn't sure where to start.  Thanks!

[adriandg]

Are the domains owned by the same central agency?  i.e. is the registration information identical?

Also, are the domains hosted on the same hosting and share the same IP?

If either of the above are true i would say the short answer would be "don't do it"

If both of the above is false, then i would choose which site you want to have the most authority and send links from all the other sites to that one site.  I would avoid crosslinking unnecessarily between all the sites.  Overall i would work towards a 'natural' linking structure.  Try to find believable reasons to cross link between the sites.  If you are talking about elephants on one site in a blog post and you have another site that is all about elephants than that would be an excellent oportunity to crosslink.  Do it naturally.  I can't emphasize this enough.