On the following site, scroll down and click on #1 in the list section (Taxonomy Changes) to get the most up-to-date list of AOU's current checklist for North American species.
One new split that I was unaware of is the Blue Grouse into the Dusky (interior) and Sooty (Pacific) Grouse. Actually, I think I heard about this a while back but forgot about it until rereading this list. This is interesting as Sibley's Guide to birds states, "Two populations intergrade broadly where ranges meet." However, the two species have different displays and new genetic evidence was probably made available for the split (I'll have to investigate this further).
Another is the Tufted Titmouse into the Tufted Titmouse and Black-crested Titmouse, which were once considered separate species, then lumped, and now split again. This has also occurred with the "Northern" Oriole fiasco which is now put to rest with Baltimore and Bullock's Orioles considered separate species. However, once again, Sibley states, "Intergrades are frequent in narrow zone where ranges meet in central Texas," with a complete range of intermediate birds. I'm not sure what new genetic evidence has garnered a split for these two species but it is interesting to see once-thought subspecies being split despite common occurrences of hybridization. More on this to come.