Early in the morning I cracked my copy of Maclane and Moerdijk for the billionth time and tried attacking the chapter on sheaves again. For some reason the idea of the germ of a function is sinking in now.
Finished Ned Drew's "By Its Cover", which introduced me to the book-cover design work of Lustig and reminded me that yes, I love Chip Kidd's and John Gall's stuff, I like Salter's and Dwiggins's, and I think Rand's (at least insofar as book covers --- not sayin' nothin' about all the rest of his work) is way overrated. With the exception of "Thoughts on Design". That one's lovely.
Also I've been looking at the Structure and Interpretation of Classical Mechanics, a completely awesome and freely available book that does calculus with functions done "the right way". Thanks to gustavolacerda for telling me about it.