Technorati.com ranks blogs by their influence through linking. Influence comes by
a) Writing good stuff that others pick up on and link to.
b) Linking to good posts. Commenting is good, so is picking up something, highlighting it to your readers and interacting with it on your own blog.
Mine is messed up at the moment due to the recent URL change, though they only consider the last six months so that'll right itself in time. So my ranking is currently 179,694 and 59,167 - probably should be more like 100,000ish (98,472 on Sept 18th). I thought I'd see where my blogroll ranks... Influence, reader quantity and content quality aren't necessarily related. These just cover the current ** blogs by technorati influence which are the ones I read most. Brits in bold.