An online book (or $2.99 pdf) on learning python. Looks interesting. Smart name.
A nice article on how to mod the hell out of gedit to make into a pretty powerful ide. Some really good plugin recommendations and some custom code. Nice job. :-)
An HTML entity lookup service. Type in part of the name or character and it'll show you the options. Useful.
symfony is a powerful PHP framework. It has some very impressive scaffolding (CRUD interface) tools, is highly customisable, and designed for enterprise level programming. It looks good for crud related projects, perhaps not so much custom projects.
A post on pimping Gedit to make is something like Textmate (proprietary mac editor). Includes tips on some useful plugins and how to tweak settings. Worth checking out.
An overview of various editors for Ubuntu Dapper, focusing on Ruby on Rails compatibility. Each editor is covered in a little detail with enough information to get a flavour of it. Useful.