We had a scenario where SharePoint was installed on Domain A and the users whom accessed SharePoint where from Domain B.
This will work most of the time until you start doing things like People Picker in SharePoint and configuring profiles, my sites etc.
There is some more work for that to happen as listed below
1. To get people picker working correctly for users from other domains you need to run the syntax stsadm -o setproperty -pn peoplepicker-searchadforests -pv domain:domain1.com;domain:domain2.com,domain2\user,password –url https://sharepoint.domain1.com (good guide on this http://www.gk.id.au/2009/04/people-picker-sharepoint-and-forest.html)
2. To greet people from the one-way trust domain by name in SharePoint and to enable creating my sites for the other domain users , you would need to import the profiles of the users from the second domain. You need to do this by going to shared services providor - User Profile and Properties - Configure Profile Import (at the bottom of the page)
Once on that page, choose custom source and create a new source for the AD (example of syntax to use for the custom source can be found here or just google http://miss-sharepoint.blogspot.com/2008/04/custom-source-in-profile-import.html)
3. If you also want the one-way trust users to have their own "my site" then you need to change the app pool account that your my sites web application uses to an account from "Domain B". This is because since it is a one-way trus between
Domain A <- B, a domain account in A will not be able to talk to B but in order for my sites to work, my sites app pool accountconnects to the domain where the user is from to get the information related to the user but it will work the other way round because B has a one way trust with A.
So create a domain user account in Domain B and through Central Admin update the App Pool account that my sites uses to the Domain B account.
Finally add that app pool account into the farms administrator's group to complete the process.