Internet

Inspiration
Deviantart - The largest collection of quality artwork around. Huge database and community.
FFFFound! - Constantly refreshing list of somehow noteworthy images.

Advertising
AdsoftheWorld - My daily lunch of quality advertisements. 
Joelapompe - Copycats are active in advertising too and not everything is creative, see it here.

Designing
CreativeBits - All topics around designing and freelancing are discussed here. Also Mac orientated.

Downloadables
BrandsoftheWorld - Logos of most big companies are available for download here in eps format (free!).
DaFont - Most famous font site I presume and quite right I'd say.

Information
Alexa - Get statistics about other websites including registration details, link backs and ranking.
Google PageRank Check - See how high your site is rated on importance by Google.

Services
Analytics - Undoubtedly the best analytics tool for your website. Analyses your visitors.
Browser Size - Very simple tool to show what percentage of web users can see your site without scrolling.
NetRenderer - See how your website works in other (old) browsers without actually having them installed. 
One.com - My webhost, I'm really satisfied with them.
Photobucket - Good quality service for uploading pictures (and videos).
WhatTheFont! - Genius site for when searching a font. Simply upload an image containing the font.

Other
Clients from Hell - Stories contributed by designers about horror clients.

Personal
Twitter - My Twitter profile.
Facebook - My Facebook profile.
Hyves - My Hyves profile.
Deviantart - My Deviantart profile.

Books

Advertising
Hey Whipple Squeeze this! - By Luke Sullivan
Essential guide about advertising.