It looks like pMachine will be releasing their longed-for ExpressionEngine developer documentation soon. If you’re a PHP programmer, and you’re using EE, then you’ll be interested in this release.
I’ve been thinking of making my own module before, but two things stopped me: I’m not a PHP guru (yet) and no developer documentation. I have already written four EE plugins, but there’s no money in them. Modules, on the other hand, can be just about anything and can be large enough to charge money for.
I’ve recently purchased PHP Cookbook from O’Reilly and it has a LOT of excellent stuff in it. I hope to expand my knowledge of the language and become good enough to write excellent modules for EE, and hopefully make some money.