I've been playing with Hotspot Finder from iPass, which, as you might already be guessing, helps users find iPass' APs, which the company bills as the world's largest commercial Wi-Fi network. I wish I'd known about this during my Baltic mobile unified communications project; given what turned out to be the company's extensive availability, I might have been tempted to violate the rules of the project (free access only) to give iPass a turn. I've actually used iPass in the past, but Hotspot Finder clearly makes the process much easier. Give it a try.
Of course, it's also fair to ask how one might find the location of a hotspot when not connected in the first place. I've been using the Web-based version of Hotspot Finder, but there's an app as well (see the client link below) that includes offline discovery. It might also be nice to use cellular data for this purpose, with the user's permission, of course, so as to avoid needing an app, but as the cost of cellular data while roaming could be, of course, astronomical, the app really makes a lot of sense.
Especially since it's coupled with a connection manager, iPass' own client in this case. While I'm assuming that the Wi-Fi Alliance's Passpoint initiative will eventually make connecting to a preferred Wi-Fi operator, like iPass, absolutely transparent, connection managers will continue to be with us for some time to come. More on Passpoint in the coming year, but, for now, let's face it - cellular-like, transparent, automatic connection to Wi-Fi is at least a couple of years away.
iPass also publishes a number of interesting reports and analyses on a variety of topics; of particular interest is the Wi-Fi Cost Index Report that studies how Wi-Fi can significantly reduce mobile communications expenses, but all of their documents should be on your reading list.