Webform Remote Post is a module that works along the Webform module. It eases the integration between Webforms and other web applications (including systems like Salesforce and Eloqua).

Adds functionality to the Node Expire module.

Really rad developer module. Use this in addition to Devel to become super awesome. One thing I like about it is the ability to clear any cache you want; you can clear the cache from just one view, for example.

This module lets you take the input from a field and allows using HTML and token replacement (or alternately PHP) for display.

Developing with Apache Solr? Then you pretty much gotta have this installed. It will show you the entire Drupal Solr entity in a subtab next to the normal devel subtabs.

The only thing I've used Schema for is for easily seeing the differences between what's in the db and what Drupal expects to be there. Very handy for cleaning up a dirty db :) This module can also be used to do all sorts of other db related stuff and has an API used by other modules.

Easily create a scaffolding for a module. Gives a nice UI with a full list of hooks to be included, all organized into collapsable sections. Try it out. It might save you some time.

"It allows a user with the right permissions to switch users."

This module shows if Drupal or any of its modules have been changed. If you have the Diff module installed, it will show you the exact lines changed.

This is the module that is used on this site for code highlighting.