This may be old news for most (or all) of the regulars 'round here...
I've had Tennant's idea of Phoebe & Ross buzzing in my head for a while, and the more I think about it, and the more I watch the show, the more I like it. I was once firmly in the R&R crowd, but the writers have done irreparable (sp?) damage to that idea, and show no proclivity towards a good building up towards a reconciliation. So, with Tennant's (unknown) prodding, I've been watching the eps, particularly the last few seasons, with an eye towards R&P interaction and chemistry.
My conclusion: they would make an interesting couple. Obviously, the baggage that exists from the R&R debacle would make things complicated, and an R&P relationship would work better without that, but...
Using Phoebe as the common element, I've also noticed something else: Phoebe doesn't like Chandler very much. Sure, they're friends, and she cares about him -- they had some nice interaction in Season One, but the last few seasons, it's become apparent that Phoebe thinks Monica could do much better and that Chandler is the least regarded of the five to Phoebe.
I realize I don't have all the specific episode references here, but that's what y'all are for. :-)