Suggested Features:

Janrain (Drupal module) and Recaptcha/Egglue Captcha (Drupal module) Integration
On the main page of my site, you can see options to login with:
-OpenID
-Yahoo! Accounts
-Google Accounts
-Twitter Accounts
-Windows Live ID
-AOL ID
and LiveJournal.

Egglue is a semantic captcha that is probably harder to bypass than standard captchas.
For example: "Knives can _______ butter."
Solutions: Cut, Spread, Slice...

Forum Improvements

My own website uses the Drupal forum system, and I've customized it with CSS.
I added rounded corners and drop-shadow, and it certainly made an improvement.
I also added the Wysiwyg Drupal module, with the NicEdit content editor. ( http://nicedit.com )
See: http://openzest.com/forum and http://openzest.com/node/17