If you've found a bug in one of the extensions or you think something is missing you can file a bug (you need a bugzilla account for mozdev.org. To create one, just follow the previous link).
Of course you could also leave a message in the treads on the MozillaZine Forums, for more discussion with other users:
For extensions localisers who want to translate one of my extensions, the latest versions containing the most up to date localizable strings (sometimes not even released yet) can be found at Babelzilla, the centralized extension localization forums:
Finally you can contact me for other things (not spam!) or if you want to keep your message more private at twan__(some rubbish)__no@gma__(more rubbish)__il.com
This section is for people who can spare some money, and want to support the development of my extensions: Don't donate if you don't enjoy my extensions or if you can use the money for better objectives.