You probably know this but in GMail you can set up keyboard shortcuts for operating without the mouse. And I always forget which keys are mapped to what (for the more obscure things). I then found out you can bring up key help at any time by hitting '?' (hint, not while you're writing an email - that would just put a ? in :-)
Ok, not that interesting, but if you hit '?' in Google Reader you get an equivalent help overlay. Give it a try - I get about 300 new articles a day and using the shortcuts allows me to get through the ones that don't interest me to the gold in seconds.
Eg scan all the Age newspaper articles for the interesting headlines in about 20 seconds.
j,j,j, (skip over some articles),
m (ooh, i'll read that later)
j,j,... (keep skimming)