"File entity provides interfaces for managing files. It also extends the core file entity, allowing files to be fieldable, grouped into types, viewed (using display modes) and formatted using field formatters. File entity integrates with a number of modules, exposing files to Views, Entity API, Token and more."

I just read a great article on this that breaks things down very well. You can find the original article here: http://fredparke.com/blog/create-your-own-tokens-drupal-7

Basically, you need to use two hooks. The first one tells the system about your token. The second one contains the specific logic for your token.

"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)

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."

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).

An example module which integrates the Flag module with a custom form.

Gives replacement tokens. This module is used by so many other modules, you are sure to use it and learn it if you haven't already.

"Define dependencies between fields based on their states and values. "