Sender Policy Framework (SPF) is an open standard that aims to help prevent spam, and stop legitimate email from being tagged as such. While the specifications can take some time to understand, there are some web-based tools to help you make creating your SPF records a little easier than by hand, but I still find them to be a bit misleading. According to the SPF FAQ the simplest way to create your SPF record is to simply list the IP addresses of all servers that mail goes out through, e.g.:

Lynda.com, purveyors of fine video-based training materials, have just released a new tutorial for Ruby on Rails. Totalling over ten hours, it seems to cover everything from the basics (installation) to slightly more advanced topics like dealing with multiple databases. Should be good!