Q:

Can you have lookup column to rich text field

Can a SharePoint 2010 lookup column point to a multi-line rich text field in another list?  From what I'm reading, it can only see single-line text fields in the other list, which limits its use in our case. 
What we need to do is pull a rich text field from another list and show it in the first list, but filter it somehow.  So a certain item in List 1 will show a rich text value from List2.  If you know of another way to do this, we'll use that instead.  

A:

No, not that I've seen even in 2007.   There are 2 options that I can see. 
Use a lookup column (point to the title field or something similar) and a workflow on item creation that pulls the data from the associated lookup list that copies the rich text field into it's own rich text field. 
Or just use a lookup field (point to the title field or something similar) and use a linked datasource and a dataview web part with joined subviews to display the data. 
The second option would be "better" in that you aren't duplicating content and you don't have to worry about trying to keep data in sync.   Marc Anderson has a good post on joined subviews in DVWPs.