We don't currently have anything like this listed on our website but I can tell you a few:
CSS Form Builder replaced Validation Toolkit.
Pro Maps for Google replaced the mapping part of Dreamweaver Tools for Google although the latter is still available with other Google features in it as a free download (on the download page - extensions tab).
SiteAssist Professional replaced SiteAssist.
DataAssist replaced Database Search.
Dynamic Web Charts replaced Dynamic Flash Charts.
I think that covers the majority of replaced extensions in the last few years. Anything not listed on the tabs of the extensions page and downloads page would have been discontinued. Constant Contact is the only extension we are currently not selling that we have definitive plans to bring back.
If you have other specific questions, please post back and I will answer them since we don't have a better way of providing this information at this given moment.
