Links.

Other (Potter) icon sites we've found:
The Aviary - A whole slew of icons from various series, including Potter, obviously.
candy from strangers - A site with free use blank icons, exclusively and extensively Potter.
Dapper Designs - A mixed bag of very slick-looking icons, with a separate page for Potter.
//DRACO//NOCTIS//DOT//NET// - Small, but lots of good stuff. Exclusively Potter. A must visit.
hipsquares - a small Livejournal icon community which emphasizes individual style. [ICONIFY] - Icons in many different sizes, from Potter and elsewhere.
Nixxie's Iconorama - Huge, huge, huge site of Lord of the Rings and Potter icons, blank and with text, free for use and tweaking. Another must visit.
Snaples' Icon Site - Small, but pretty, with blank icons for the tweaking.

(Some of the) image sites we use.
The Council of Elrond
Ioan Gruffudd Home Page
Jamie Bamber, this is your website
The Leaky Cauldron
The Snitch.co.uk
Horatians.org
Two Evil Monks
Moon Jaguar's Hornblower Screencaps

Fonts, Programs, Etc.
Download.com - Fonts, demos of graphics programs like Paint Shop Pro and Photoshop - it can all be found here.
04 extra bitmap - For small icons, one needs small fonts.
1001 Fonts .com - Free fonts. Lots of them.
Acid Fonts - More free fonts.
CarpeSaponem Fonts Portal - For the two freeware Potter fonts, Lumos and Parseltongue.
The Font Foundry - Free and shareware fonts. It has a download basket, which Tinderblast thinks is nifty.
Larabie Fonts - Free fonts made by Ray Larabie.