[ihavenomouth]

Under level 15 or buying your first home? Leg Up Negative Interest Bearing Microloan Service | Groups | Glitch

Glitch Academy Much better than the old skill queuer, this allows you to enroll your Glitch in 'classes' and basically learn things in a certain order, constantly, even if your computer is turned off.

agent86's tools home! These are priceless.

GlitchUr | Just another WordPress site

Pro Tips for Newbies and Pros alike | Forums | Glitch

A Guide to Giant Philanthropy 101 (Shrines, Donations, Favor, Icons, Emblems) | Forums | Glitch

Explanation of Skills! (Particularly those tricky plant-related ones) | Forums | Glitch

Callout system for Ajaya Bliss

Cubimal Value List | Forums | Glitch

Scripts
ping (glitch) - Userscripts.org Auction+ info, Achievement Checker, @reply and quotes, and sorted realty.
glitch-location-checker - Glich Location Checker - Google Project Hosting
Unofficial Browser Extensions - Glitch Strategy


Where to find stuff:
Ur | Zog's Glitchy Tools
The Glitch Resource Database

Bit more helpful stuff:
Third-party apps/sites | Forums | Glitch
Energy, mood and profit (currants) from food/drinks | Groups | Glitch
Money Makin' | Groups | Glitch
Glitch Info - Locations List

And especially:
Unofficial API Tools - Glitch Strategy
and Glitchpedia.com - Home

Keep up with changes:
https://twitter.com/#!/glitchlog

For fun:
The Glitchen Imaginatur | A Publication of Triskaidekamedia – not affiliated with Tiny Speck, Inc.
Resources... | Groups | Glitch (Most of these links are for fun, but it also includes the link to the wiki!)
Frustrated Pumpkin | Forums | Glitch
The Giant Picture
The Lazy Cubimal


That's everything I can think of right now. Hope it helps!