Over at my new journal, I've posted 62 reasons why I think Robin is Barney's bride (including some speculation and three minor spoilers). I've clearly marked the spoilers, so you can easily avoid them if you want to remain unspoiled.
Part 1: Reasons 1 - 39
Part 2: Reasons 40 - 62
UPDATE (1/3/12): I've added some things to numbers 16, 29, 40, and 55. I also added a 63rd reason and modified numbers 35 and 46 to hide only the spoiler bits rather than much of my arguments.
Thanks so much to everyone whose taken the time to read my posts and to those of you who've commented!