Hello, here are three little extensions that we are using on our sites:
A simple contact page form
A module that transforms bits of text. Currently serves only to parse youtube urls and set a youtube iframe instead, but the very simple API can easily be extended. Yes, I know about the bbcodes, but I think it's easier to tell my client to just paste a full youtube url without tinkering with details.
This is actually two additions: one, the URLField is a field that has validation for URLs. The second, ExternalLink is a dataObject that is a URL. The first one is useful to validate URLS. The second one to attach external urls to a dataObject (for example, user links on their profile, client links, projects links...)
Hope they are useful to someone.