There may be a list of this somewhere, but I’d be interested in your top 5 or so UR titles. If you were putting together a list for someone inquiring into UR, what would they be? Sources available only online count as well.
Let’s go ahead and list the following three (which I think are the best recent works):
The Inescapable Love of God by Talbott
The Evangelical Univesalist by MacDonald
Universal Salvation? The Current Debate ed. Parry/Partridge
Got another 5 titles or so?
Tom
What about The History of Opinions on the Scriptural Doctrine of Retribution by Edward Beecher? Top 5?
I’d add:
The One Purpose of God by Jan Bonda, though after about the first 1/4 of the book (which was very readable and powerful) it goes through Scripture with a fine (reeeeally fine)-toothed comb which is a bit cumbersome, but still great if you have patience.
I had to do so much of this by myself to begin with, I don’t really have any recommendations, aside from MacDonald–and his theological works aren’t primarily about universalism. Poor John Piper managed to get all the way to the sermon on “Justice” in volume 3 before realizing he was reading an anti-Calvinism work!–which doesn’t say much for his reading comprehension skills. 
Or, perhaps it says that much more about MacD’s utility for all Christians. (It’s also possible that Piper was reading snippets from a digest, like C. S. Lewis’ famous collection of MacDonald quotes.)
So, I am certainly paying attention to lists and recs. When the time comes to begin work on a systematic theology tome, it’ll be especially nice to have a number of prior reference works for double-checking from. 
I’ve mentioned it before, but a good “transition” book, IMO, is “What Does the Bible Really Say About Hell? Wrestling with the traditional view” by Randy Klassen. I think it’s a great resource for people who kind of need a bit of a roadmap on how to get to CU from the traditional position.
Thomas Greggs, an Oxford Theology PhD has written an excellent theological study titled Barth, Origen, and Universal Salvation it is quite interesting, and gives some fascinating insight into Origen’s thought on salvation. However, this is not for the newcomer. It is a text written for theologians and philosophers of religion (I’m in the latter class). So, background study will be needed.
Ooh. Sadly, the Greggs book is not available from Amazon…
(I wonder who’s writing the chapter on Barth for Gregory’s essay collection next year…?)