The third of the "Big three" upstream providers that you need to look out for is InfoGroup. Between them, those three push to a lot of different places.
I also consider Citysearch and Superpages to be fairly critical in a semi-upstream kind of way, as between them they feed to a fairly large number of platforms. There's also a suspicion of some kind of stronger relationship between them and Google Local -- this speculation comes from my own experience of how quickly an incorrect listing or reviews show up in Google from these two platforms. I think it's also mentioned in the local search ecosystem outline put together by David Mihm. I'd highly suggest looking that diagram over, because it's a great way to get your head around the relationships. The most recent version I know of is here.
Travis and Miriam, I will definitely follow up on the local visibility thing and report back. Yahoo! is currently pulling together the local data from my own company, which serves as my guinea pig. I also have a client in the middle of an address change, so there's reason for me to give it a shot.
Reading up on it, I kind of suspect (but am not sure) it's going to be more of a UBL type of service offering than a Yext one (e.g. it submits, rather than having an active connection). I'm incredibly leery of these services, as we've seen some absolute disasters come out of UBL when information is entered in a slightly different way.
In terms of streamlining things, Travis, you're struggling with something that I've been trying to systematize more efficiently in our business for the past few months. We generally use a plain old spreadsheet to keep tabs on everything. It works, but it's not the most amazing solution. The issue that we face is that clients in competitive local search niches that need a wide range of citations. When you get to a certain number, it's quite rough to keep it all together, and maintain forward movement.
Here's our experiences with three different services (so far) that are all meant to help the citation building process:
Places Scout
Provided a massive amount of data and a huge list of citations, but very little in the way of managing (e.g. tracking) these. I couldn't figure out a way to filter out what we had already got, so we ended up doing a lot of double work going back and checking them against our list, or going to the site they recommended to check that. There's a massive depth of info within the tool (beyond citations) but it feels clunky, and the reports it outputs are not of a quality I'm comfortable showing clients. If you've got the time to fix reports (or don't need pretty ones) it could be worth it. It's $197/year, so not overly pricey.
Whitespark
Much better interface, in my opinion, and probably the most commonly used tool to track down citations. This has been our go-to tool for the better part of 6 months for building citations. My only beef: I can't find a way to mark a citation as "Pending" or "Needs action" so I'm back to the spreadsheet.
BrightLocal
Something we are looking into due to its local search rank tracking. (Sorry, SEOmoz, we love you, but your local rank tracking is confusing to our clients.)
We're experimenting with this currently. Doesn't seem to go quite as deep as Whitespark (but I'm comparing two different businesses, so that's anecdotal evidence), but provides slightly better management of whether or not you have a listing. It offers "Got it" "Pending" or "Potential" options, so you can at least tell if you've taken action.
Unfortunately, all three require that we keep a separate spreadsheet that details login information and notes.
Wow, long response! Hope this helps, rather than putting you to sleep on your keyboard.