The Internet is a huge place; it wouldn't make much sense to try to provide an exhaustive list of links here, so this is just one or two links you may find interesting.

Webcomics

• XKCD, xkcd.com, describes itself as “a webcomic of romance, sarcasm, math and language”. Extra funny, geek-oriented humor, often with surprisingly insightful commentary on social interaction and relationships. Don't forget to let the mouse hover over the comic image.
• Piled Higher and Deeper, phdcomics.com, a hilarious, sometimes cynical view at trying to work towards a Ph.D.: Procrastination as a way of life!
• A Softer World, asofterworld.com, sometimes funny, sometimes bitter, very often surreal, politically incorrect, at times even slightly disturbing narrative on top of great photography. You have to see for yourself. Kudos to Kornilios for sending the link.

Last.FM

Last.FM is an amazing music-related site and associated user community. Download the appropriate plugin for your music player and start keeping track of the music you hear. There is support for hardware players as well... for example, iSproggler allows you to synchronize the “Recently Played” playlist of your iPod to Last.FM's database. You're bound to become addicted as you browse through your listening habits and discover new tunes to listen to, based on the community's musical collective consiousness. Here is a Flash-based “Top Artists” quilt for my Last.FM profile:

Facebook

You're not expecting me to introduce you to Facebook, right? :-)
Here is a link to my profile.