What's acceptable for self promotion of semi/non related sites?

[Asia_Expat]

I'm about to launch a couple of satellite websites to my main website. Lets assume the name of my site is Asia Expat (it is not).

I am running and adserving system on another domain, which I will use as the platform for my ad inventory and advertiser interface. Lets call it 'Asia Ads'

The other website I am launching is the promotional tool I will use for my web design business. Lets call it 'Asia Design'

They are only related in the sense they are targeting an audience/client base in Asia and they have an overall theme and look that matched the overall brand of my web presence.

I want to interlink the sites in some way that does not violate any search engines rules. I am aware there are many threads about this issue but frankly, I'm hopelessly confused.
I don't see what is wrong with me adding some links between the sites I own, stating that 'Asia Expat' is designed and maintained by 'Asia Design', or that the ads on this website are managed by 'Asia Ads'... and in reverse, one of the sites we manage is 'Asia Expat'

They will likely all be on the same IP address.

[Receptional Andy]

I doubt you will run into any particular problem with this type of interlinking, especially if the content is different across the sites. You may not see as much search engine benefit as if the sites were not essentially the 'same' source. I've never had sites interlinking in this way run into any problems.

Of course, your mileage may vary, and you'd be wise to ensure there are no factors on the site that might not stand up to scrutiny, or combined with the interlinking might push one site or another over the edge.