"Maxlength allows you to set maximum length of any field on any form making use of the form API. This includes fields created using the UI. (Example: any text field on a node)

"Geofield is a module for storing geographic data in Drupal 7. It supports all geo-types (points, lines, polygons, multitypes etc.)"

"This is a very simple module that adds a 'weight' field to the tables already used by the excellent Flag module. This weight can then be used to provide ordering of flagged items. This module also provides a Views field which can be used to sort flagged items. One interesting use of this ability is to integrate with Draggable Views to create a user-sortable list of flagged items"

Make all external links open in a new window. There are optional custom exclude/include filters.

From the project page:

Open source video solution.

Used on http://drupal.org, "This module stores the changes of a node into a field attached to comments allowing to display a kind-of activity stream on the node much like on drupal.org issues just with a lot less custom code."

There is a great article that shows how all of the Acquia sites are architected. In that article, it is mentioned that Services is used quite a bit to power REST endpoints. Here is a really, really, useful tidbit that I don't want to forget which comes from that article.

Lets you use tokens to embed video and have the ability to add a button to the WYSIWYG for easily adding a video (for those to0 lazy to type).

Flag is the ultimate bookmark tool. A must learn module.