Packagist is the main Composer repository. It aggregates public PHP packages installable with Composer.
A SilverStripe composite field for having various link types *with title*, in a single field with a nicely styled form.
A Silverstripe UploadField that supports (very) large uploads without fiddling with php.ini
Various admin tweaks & enhancements
Extension to hide pages from the SiteTree
Extension to quickly add a (set of) featured image(s) to a pagetype
Even smarter automatic image cropping for SilverStripe
Stand-alone latlong field, abstracted from mappable or a comparable module