C3P0 had a memory wipe, but R2-D2 and Darth Vader never had their memories wiped. Both were terrific friends. Did they ever interact with each other again?
Within the established Disney/Lucasfilm canon (the six theatrical movies, Clone Wars TV series, Clone Wars film and Star Wars : Rebels TV Series) Darth never spoke with R2D2 again, although they did briefly interact in 'A New Hope'.
A New Hope :
Darth just misses R2D2 on the Tantive IV.
They're both on the Death Star at the same time but it's reasonably clear that they didn't meet, even for a polite lunch.
They're around 50 yards from each other during the trench run. Vader shoots at Luke and inadvertently hits Artoo in the head. Awkward.
Empire Strikes Back
Darth just misses R2D2 during the Hoth escape.
They're both (briefly) in Cloud City together. Once again, they fail to meet up, even for drinks or a chat. Possibly R2D2 is still sore about the whole "shot me in the head" thing.
Return of the Jedi
They're both on the surface of Endor during the rebel assault sequence. Once more, they fail to touch base. At this point it's looking almost deliberate.
They do have the opportunity for a tête-à-tête at the very end of the film (back on Endor) but unfortunately Darth Vader is dead and hence not much of a talker. My guess is that the main topic of conversation would be around the subject of "who shot who in the head" so it's probably for the best anyway.
The Force Awakens
Darth Vader is dead anyway. Only his helmet survived which can't interact with R2-D2.
It's not clear whether R2-D2 can see a force ghost.
Star Wars Comic
As of April 2014, the comic serial is now considered part of the main Star Wars canon.
In Book 1, Part 2 of the New Marvel Star Wars serial, both Vader and Artoo are on Cymoon 1. At one point, Artoo is in an Imperial Walker that attempts to stamp on Vader. Once again events conspire to prevent them from speaking to each other.