httpwebwitch - 8:42 pm on Sep 9, 2011 (gmt 0)

this produces something not-too-bad:

strtoupper(base_convert(microtime(true)*100,10,36))

the result is codes that are not strictly sequential, but they act like incrementing numbers. Here are some, taken a few seconds apart:

1OFRH7H9
1OFRH7XF
1OFRH8ED
1OFRH8WY
1OFRH9H0

They don't feel entropic enough to me