Wikipedia - Wikipedia has excellent articles on many exoplanetary systems. Links here can be considered the "main" outside link for the planets on this mini-wiki. Each system found here should have a prominant link to a wikipedia article. This wiki is intended to have a style much different than wikipedia. Wikipedia should contain encyclopedic articles and standardized info boxes, while Exoplanetary Scratchpad should contain raw (yet organized) information, like links to news articles, other websites, blogs, message board threads, galleries, and bullet-styled notes.
Extrasolar Visions - The "roots" of this wiki. Contains visualizations of many planetary systems. Has a [forum http://www.extrasolar.net/forums/] with a strong exoplanetary community that continues after the passing away of the website's founder John Whatmough in 2005. Many of the pages here were originally posted on the message board as "System of the Day" posts.
The Extrasolar Planets Encyclopaedia - The source and authority for informations on exoplanets used by Extrasolar Visions and this wiki. Contains links to papers related to each planetary system.
Sol Station - Has very detailed article pages on many nearby star systems, many of which contain planets.
Planet Quest - NASA's official exoplanet homepage. Contains the "New World Atlas" catalog of planets and news articles.
Astro Cosmo - Portuguese site with articles on many planetary systems. Here is a link translating the site into English
Systemic Backend - Characterizes extrasolar planetary systems and includes "unofficial" discoveries