Websites of practical use

The Anomalocaris Homepage
Information about various anomalocarid species.

David J. Peterson's Web Thing
Provides numerous constructed language examples; interesting as art and instructive for language construction.

Grammar of the Novegradian Language
Among the most horrifyingly well-developed constructed languages found online.

Useful projects

Galaxy Zoo
A website allowing one to participate in galaxy classification and other crowdsourced scientific endeavours from one's computer.
Wikimedia Contributions

A more complete list of links