Completely unofficial, and so not quite the inside scoop you might wish for (as it's written by people who use the Tube, rather than any of its staff). But plenty of promise as it grows in popularity. "Things I'd like to see on the Tube: a penalty ticket inspector who isn't a sadist; a Photo-Me booth you can fit more than a mouse into; a District Line train that doesn't stop between every stop." Also full of "Tube rules" (how to sit, how to dress, how to ignore the weirdo in the carriage). Sprawling (so you'll need to wait for the page to load) and enjoyable, and written by someone who - gasp - is not afraid to ring up, say, the people who devised an advertising campaign based around the Underground and ask them why."
Check out the other 11 blogs here. And many thanks to the teccy journalist Charles Arthur for selecting us.