Here is a list of links to webpages I visit. Some are useful for productivity, others are useful for procrastination. Some are a mixture of both.
http://www.pastormelissascott.com – Bible teaching without a bunch of religious BS.
nLab – The nLab, a reference and wiki for n-Category stuff.
Azimuth – a much better maintained blog than this one that deals with many interesting topics.
TeX stack exchange – If you have a question about LaTeX, odds are it’s been answered here.
Brown Sharpie – “Mathematical Cartoons inspired by Sharpie Fumes” ~ what update schedule?
xkcd – Stick figure comic for nerds ~ MWF. The what-if spinoff updates Tuesdays.
Abstruse Goose – That other stick-figurey comic for nerds ~ weekly?
Project Euler – Series of problems that are aimed for using a mix of mathematical insight and programming.
Homestuck music – Official music for a webcomic. Mostly instrumental.
Homestuck fan music – Fan-made (i.e. unofficial) music for the same webcomic. Also mostly instrumental. Some of my preferred music to grade to.
MSPA – The webcomic the previous two links were spawned from. Very long; currently in hiatus. Read at own risk.
Saturday Morning Breakfast Cereal – archive binge at your own risk ~ daily.
Spiked Math – Geometric-figure comic for math nerds ~ “epsilon times per month for some epsilon > 0.”
Piled Higher and Deeper – Often hits disturbingly close to home ~ MWF?
There are at least a bazillion other webcomics I read. I’ll add them in later.