With the Byteplant Phone Validator plugin you can easily verify if a phone number is really valid and callable (http://www.phone-validator.net).
ZWS Contact is a simple and lightweight wordpress contact form plugin.
This plugin detects temporary email addresses like mailinator, not connectable email addresses and helps to keep the userbase and comments clean.
This plugin makes Thickbox CSS compliant.
Checks comment to ensure they are longer than the minimum, shorter than the maximum and also allows comments to be forced into moderation based on len