Sam in Valinor
 

Sam joined Frodo in Valinor,right?

Not exactly, The Ringbearers were allowed to go to Tol Eressea the island just off the coast of Aman.

I think I remember reading something about Sam going over the seas to join Frodo in the Undying Lands. Are you sure he didnt meet him in Valinor?

The island of Tol Eressea is as much a part of the Undying Lands as the rest of Aman, including Valinor, is. It is where, after Morgoth's downfall, the Elves coming from Middle Earth settled.

It is my understaning that the Elves of Tol Eressea remained there by choice; I have not heard it said that they were barred from visiting their kin on the mainland of Aman. It is likely that Bilbo, Frodo and Sam, having settled with the Elves they knew, would have visited Valinor, if only to see Gandalf again, who I'm sure would not remain on Tol Eressea for long.
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Perhaps this older thread about the same topic might interest you, Letty!

Sam's final journey

And yet I want to believe that Sam and Frodo found each other again before the end. It would be so unfair if they didn`t...

Interestingly enough, Tolkien wrote, as early as 1944 (about ten years before the official publication) that he intended for Sam to remain in Middle-Earth.