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		| Another foil apparent, however, could be Denethor/Theoden. | 
	
 Just my unenlightened opinion, but I believe that two foils would have to interact with each other. In the book we never see these two even meet, and I question the nature of their relationship (since they have none!) as being that of each other's foil.
As for Gollum, I think that comparisons with Bilbo work better than with Frodo. As for the initial question, is there a connection between Frodo and Sauron? 
Yes. The One Ring. Are there any further connections? 
No.