Well Ultimate Guitar is good, but I usually work it out by ear, unless for some reason i'm in a mad rush. It's really good for your playing, I spent about 1-2 hours a day for a few weeks just downloading random metal-ish songs with cool riffs and working them out, it's a cool skill to have, although i'm not perfect yet, by all means, but I can do it fairly quickly, and then you can be sure it's right, and if need-be check it against the tabs. :) Also handy if you can't be bothered to tune into some strange tunings some bands seem to have :)