Sign and Encrypt (GPG) from edit menu

There are no plugins that do this. Writing one is doable, though probably unnecessary. You can configure gedit to sign/encrypt documents using the External Tools plugin and adding an action for gpg. For example. I just setup a Clear sign action that appears in the Tools menu:

* Enable External Tools via Menu > Preferences > Plugins External Tools
* Choose Menu > Tools > Manage External Tools
* Add a new action named "Clear sign"
* Set the script to
#!/bin/sh
gpg --clearsign --no-tty -
* Input: Current document
* Output: Replace current document
* Close the manager window
* Type any text into a new document
* Choose Menu > Tools > External Tools > Clear sign (may need a restart to see this)

With Natty 11.04, seahorse-plugins can still be used. It's then available in gedit plugins en-decryption.
The plugin isn't available in Oneiric.
Bug #832888
Bug #796752

Alternatively Nautilus scripts e.g.
http://gnome-look.org/content/show.php/Encrypt%2BDecrypt+Files?content=74653&PHPSESSID=ca227c92f6942ab84cba47c6aefd1650
http://gnome-look.org/content/show.php/EncryptDecrypt+Reloaded?content=105874

Some autopromotion/request for feedback:
http://pietrobattiston.it/gedit-crypto

It still does not sign, but it's very easy to add. I just want to understand if the interface is appreciated (I never used the old version of the plugin).