In the first year of learning OpenStreetMap users are keeping Map Features open at all times. It is too big and complex, a number of cheat sheets would be handier.
The current relation editing is too generic, and there should be a plugin specifically for editing public transport relations.
At the moment you can undo a changeset using either a JOSM plugin or a perl script. Undoing changes should be easier, like in Wikipedia: click, wait, make some simple decisions, done.
We have tools for monitoring areas and users, but some mappers would like to watch certain objects, like relations, to quickly fix accidental edits to them.
The only way you can ask a user of a changeset now is to write them a private message. It enforces negativity in the community and prevents introverts from communicating. Let's add a thank you button and comments.
Daily video feature about OSM news.
A set of scripts to make nested extracts in pbf, shp and other formats. All configurable from web interface: install on a droplet, upload config, run.
A proxy web service to query imagery providers for detailed imagery and cache the results.
A stand-alone application for extracting frames from a dashcam video and georeferencing them based on a GPX trace.
Video + GPX trace = mini-map in a corner.
Modern walking papers producing services are old and unreliable. We should have a net-independent, MapCSS-based vector printing solution.
A web interface for automatic processing of GeoTIFF and Landsat images and making a single tile layer out of them.
A website to plan a cycling marathon route and to generate turn instructions sheet and a GPX trace out of it.
A web editor for public transport routes: stops, platforms, and potentially highway or railway routes.