Called Champedia, the CO database allows you to search for characters, supergroups, powers, or missions.
Missions can be looked up by name, and pretty much just gives a little description, same as when you pick up the mission. It tells you what map to get the mission and what level the mission is for. Good if you want to know what all the missions are on a given map. Though I didn't see post-crisis Desert, Canada, or Millennium City, but I saw the sub maps of alot of those places (caves and buildings etc).
For powers, you can search by tier, or by power source, and it's nice to have on the website.
Characters look up. This is great for a few different things. 1) You can look up by level, experience points, hit points, handle, or of course, character name. At this point you can look into each character's information, from gear, inventory, power choices, completed missions and achievements, and even Rate their Champion.
I looked up how many characters there were in different level brackets, and there's 5,229 level 40 characters, 93243 level 1 characters, 213,347 between 10-19, 57,245 between 20-29, and 18,007 between 30-39. These numbers are instantly off, since the database is live, and players leveling up can quickly leave from one bracket to the next. But that's over 293,000 characters over level 10.
Finally, for the supergroup search. You can look up by group, or by group size (two biggest guilds have 250 members, No More Heroes, and M.A.D). You can sort by level or name, and you can click on each members name to see their character page. If you look up your own supergroup, you can even quit them through the website (it's a "Leave Guild" button), and if you have the privileges, you can change the message of the day from the website as well.
Overall, a good database function, that we can only hope will continue to expand.