Ryan,
I believe this shouldn't be too difficult to do... just depends on the tools you use :-).
Personally, I can recommend Visual Website Optimizer, which allows you to segment a running test to specific segment based on various conditions. Referring URL is one of them (see screen below).
However, you can then use only one variation of the page, so if you have more segments that you would like to test, you would need to:
- Duplicate the test itself,
- Change the copy in the variation,
- Set up the segment rules according to your needs,
- Follow this procedure with every segment :)
I have done this, but can't say it had much impact. It was too much work and I personally prefer segmenting based on customer data (new/existing customer etc.), where you can notice much more impact and it's also then "easier" to report since the differences are quite noticeable.
Hope this helps!