Drupal 8 Alpha 6 is out and it has a migrate module in there! It even has a few complete migrations: variables to the configuration files owned by system module.
One of the coolest features that made it into Drupal 7 without much (if any) fanfare is the Queue API. Drupal's Queue API is a pluggable system that allows you to queue events for later processing.
Ever since we launched our site re-design, we’ve had a pretty steady flow internal change requests – add links, change fonts, re-style buttons, adjust layouts, modify permissions, etc.
Form validation is an essential part of any web system. You need to ensure that the user has added valid data and if not, show them a meaningful error message. Validation functions are normally implemented in the module where the form is defined.