As part of the newly launched Lightroom 2, there is also a new SDK. In addition to the new features compared to the original SDK, this one contains a wealth of details on creating your own galleries using Lua. While I learned the hard way, from other galleries and sites, I found this explained things well. It provides a solid basis in coding, along with sample galleries.
For user help and interaction, there’s the new SDK U2U forum. You can also upload your product to Adobe Lightgroom Exchange.