I'm coming up for about 2000 lines now.... a lot of that is fairly basic stuff but some of it is crazy logic and I think it's perhaps time to take a break
I'm not sure it's the most I've ever done but it sure feels like it.
What's the most source lines of code you've churned out in a day? That excludes HTML/Markup -- you can't count that I'm afraid since it's way too easy to clock up oodles of markup. You obviously also don't count comments or white-space.
//Goes to make another coffee, sticky tapes eyes open to stay awake
EDIT | By the way, if you want to get the most accurate results without all the white-space and comments etc download an application called "sloccount" -- SLOC == Source Lines of Code