Be careful with using online generators though. Sometimes they're not secure or are scams.
This. I cannot stress enough how important it is to generate your own private keys. Please don't do it unless they support split key generation an even then make sure they are using it and not just lying.
If you have a decent graphics card, use oclvanitygen - it searches for more keys per second. Try checking out either sam7's or the Lifeboat one (the latter has improved support for AMD cards IIRC).