I've not actually tried it yet, but it looks pretty damn cool.
https://wiki.namecoin.info/index.php?title=Identity
Basically, there's a whole id/ namespace where you register your personal information, and there's a d/ namespace where you register domain names (akin to DNS). Onename is the same except they use i/ (they haven't even tried to discuss it and basically did it all from scratch to start clean)
The major problem is that you basically need a namecoin client to interact with the data... unless you use dnschain [0], which act as a HTTP-to-Namecoin and DNS-to-Namecoin bridge. Try this:
$ dig @dns.dnschain.net otokar.bit
$ curl http://dns.dnschain.net/d/otokar
both are my personal domain, delivered to you through plain old protocols. The last one even works in your browser !
Come and join us, this is actually the future. Oh and by the way I'm id/rakoo.
Anyone running a full Namecoin node (ie, anyone running Namecoin client) can register an identification.
OneName is providing a convenient web portal to this key-value store on Namecoin, so their business model is somewhat analogous to Blockchain.info's (or perhaps they have another business model in mind, who knows?).
The annoying thing is, we already have a namespace for identities, it's standardised and documented on the wiki. They came in and defined their own namespace for no good reason.