Like you said, CommunityCommons, ProcessQueue and MxModelReflection. Also:
- Encryption: will be part of most projects as a dependency for other modules, but still, if you need to encrypt stuff this makes it easy.
- OQL: if you want to inspect your data, this module enables you to use OQL queries. There is also the Reporting for Mendix module, with a gui to build queries if you’re not fluent in OQL and some other handy features, like a daily scheduled event to delete data based on OQL queries, but it’s not free.
- Deeplink: to create urls so you can put links on a website or in e-mails, even personalized, if you use (encrypted) parameters.
I’m not a big fan of using widgets. They tend to break when upgrading to the next major Mendix release and you need to put effort into styling them. Some of them are very good though:
- Dataview loader: shows a progress circle while loading data. Using this widget you can lazy load or (conditionally) refresh elements on a page or the contents of tabs.
- CustomString: this widget calls a microflow where you can build a string to put on your page. We use it a lot, but I can’t for the life of me find it in the market place anymore.
- HTML snippet: to insert custom html or javascript in a page.
- Simple checkbox set selector: to set associations using checkboxes.