OpenRA is an open source project that "recreates and modernizes" Westwood's classic RTS games on the PC by building a new engine for them and making them free to download. Why? A new engine means they can run natively on modern systems, and also means they can run natively at modern resolutions, so you can play Dune 2000 at 1920x 16:10 without a care in the world.
There's also improved/modern multiplayer, as well as a few more tweaks, like:
- A choice between "right click" and classic "left click" control schemes
- Overhauled sidebar interfaces for managing production
- Support for game replays and an observer interface designed for streaming games online
- The "fog of war" that obscures the battlefield outside your units' line of sight
- Civilian structures that can be captured to provide benefits
- Units gain experience as they fight and improve when they earn new ranks
Currently, having been in development for a few years now, there are three games supported: the original C&C, Red Alert and Dune 2000, though the team (of around 50 developers) behind it are also working on doing the same thing for the second generation of Westwood games, starting with Tiberian Sun.
Note that these remakes are primarily, at least at this stage, for skirmish/multiplayer gaming. Those wanting to play through the original campaigns — complete with cutscenes — need to know that each mission needs to be recreated in the new engine to work, and that there are hurdles you need to jump through to get movie and music files to play.
There's more info (and download links) for OpenRA on the project's site.