I've been warmly surprised by some of the general-topics things I've found on the net recently; either Google's search results are tending away from waffle or I am becoming very adept at closing tabs and flushing the short-term memory buffer. Dive into Accessibility is straightfoward and the tips mostly directly applicable. Unfortunately it has dated a bit; I shudder to think that there are too many HTML 4 websites out there that people now want to make accessible...
I slightly quibble with his advice on access keys (Day 15, p32 of the PDF), where he suggests that a stroke survivor may make use of them. I expect there are many people who struggle to make key chords, especially those having the use of just one hand.