This is a draft language for a new page that tells newcomers how to install OpenWrt. Please comment in the Fix top-level Wiki Pages issue on Github. Thanks. -richbhanover
Installing is OpenWrt is pretty straightforward, whether you want to install on a router you already own, or if you're searching for a new router. You'll want to review the Table of Hardware since it has links to the Details page for all routers that work with OpenWrt.
Note: As of September 2015, the current stable release of OpenWrt is "Chaos Calmer" ("CC" or "15.05"). The wiki is being updated to indicate which devices can work with the CC release. The previous release "Barrier Breaker" ("BB" or "14.07") release is still a good choice for all devices that do not indicate they can use CC.
There are other "aftermarket router distributions" such as dd-wrt, tomato, openwrt. It is usually possible to flash openwrt onto these devices, however details on how to do that depend on the device and the distribution you're using. Sometimes there might also be a difference in functionality offered by openwrt and e.g. dd-wrt. Sometimes the process involves going back to router manufacturer provided distribution, and sometimes it can be done directly. You should consider asking for help in openwrt forums or on freenode/#openwrt.
After you flash the firmware in your device, there are a set of steps that you should do to complete the setup of your router.
The steps will help you flash OpenWrt into your router. The remainder of this page gives background information about the various builds and releases of OpenWrt.
The stable release of OpenWrt is called Barrier Breaker, and is also known as "BB" or 14.07 (because it was originally slated for release in July 2014 - the final release was in September 2014). Use this version if you want to "set and forget" your device.
If your router is well-supported, the Details page linked from the Table of Hardware tells how to get the current stable BB image that you can flash into the router, and gives the procedure for flashing.
If the Details page does not have a direct link to a firmware image, you can go to https://downloads.openwrt.org/barrier_breaker/14.07/ This directory contains builds for the release, sorted by the CPU Target. Look at the Target column for your router in the Table of Hardware then enter that sub-directory. Check the file names for your vendor/model. If there is an image for the device, it should work. If you are successful at installing OpenWrt, please consider updating the Details page with the direct link to the build you used.
There is a next release branch of OpenWrt called Chaos Calmer also known as the "CC". It is currently in stabilization process - there are release candidate images that are mostly stable, and developers are working to fix a short list of issues before declaring a release final. If you want to help development providing feedback about these releases is one of the ways how you can contribute.
There are also trunk builds. These come as 'nightly' builds, as well as from individuals, as anyone can download the latest source code for openwrt and build their own images, with or without modifications. Needless to say, these images have usually not undergone as much testing, may contain freshly introduced bugs, and features may get added/removed as the development on openwrt proceeds. There's still a general effort to keep the source code at trunk functional at all times.
Warning: The trunk builds are not for the faint of heart. Lots of people post messages on the forum about trouble with the trunk builds. If you choose to install a trunk build, you should check the Details page for information about bringing it up. If it's not present, and you're not comfortable with uncertainty and lots of research, perhaps you should consider the (stable) Barrier Breaker release. You have been warned: http://downloads.openwrt.org/snapshots/trunk/
OpenWrt runs on lots of older routers. We do not recommend you go out to purchase a new device whose Status column includes 12.09, 10.03, 8.09, Kamikaze, or Backfire, or a release number of the form "R######". All these are all earlier firmware versions that are no longer being supported or maintained. You will be better served by spending that money on a newer device that supports more modern firmware.
However, if you have an older model router and would like to upgrade the firmware from the stock vendor version, review this information.
The 'Attitude Adjustment (AA - 12.09 final)' release of 25th April 2013 was a predecessor of the 14.07 Barrier Breaker release. This older AA build may work on some devices that cannot support the current Barrier Breaker or trunk builds. The AA release requires more than 16 MiB of RAM (check the RAM column of the TOH). http://downloads.openwrt.org/attitude_adjustment/12.09/
If your router has 16MBytes or less RAM, we recommended you use a Backfire image, since it has a smaller memory footpring. Backfire releases are at: http://downloads.openwrt.org/backfire/10.03.1/
For very old routers, you can look at the Historical Releases section of http://downloads.openwrt.org/
The best way to to check for existing support is check the Details page for your device. If there is a direct link to firmware, then someone has installed the build and made the effort to document it so that other people will succeed more easily.