I've finally got the search plugin I made last month to work for European Realms. The idea is the same, so the info in the original release still applies but I'll recap here.
This is an OpenSearch plugin, it only adds a search provider to the list at the top, not generic functionality for Firefox. Since it's done with OpenSearch, my understanding is that it might work in other browsers too. My instructions and experience are specific to Firefox though. If you still don't have Firefox, you can go get it from Mozilla.
I've approached the search two different ways, one way is to search all realms for a character. The other looks for a character only on a specific realm. I think looking on a specific realm is a lot more useful since most of us only play on one realm or at most a few. You can install the realm-specific search for each of the realms you play on and the name shows up when you pick which you want from Firefox's search box.
Apparently there are realms for Oceania and others for Korea. I think the Oceania ones might be included with North America. As for Korea, I might be able to do that one if someone who plays on a Korean realm and speaks some English can give me a URL to a character sheet on the Korean armory and a place on the Korean website to find a list of those realms. Sorry I'm not more thorough but remember I don't work for Blizzard or anything, I'm just a geeky player.
Update: I've posted a new version of this search plugin (with support for Korean and Taiwanese Realms) here.