OUYA uses XBMC for Android. To hold users over who are waiting for a stable version of XBMC (which will happen with XBMC v13), users can download an unofficial v12 of XBMC for OUYA from the OUYA store.
For brave test users, we currently recommend a nightly Android build: http://mirrors.xbmc.org/nightlies/android/
Side-loading development builds
These steps show how to side load a development build, instead of the version included in the OUYA store.
Step 1: First go to the developer section (the Make tab) in Ouya, select Yes or "okay" to enter the developer section.
Step 2: Open the default browser and then press Y on the controller to enter in your own URL.
Step 4: The download is 50.3 MB and depending on connection can take a while (1 min on 60mb/s), during the download you won't be able to tell the progress unless you have installed Chrome or ES File Explorer.
(If you have ES File Explorer you can just open after it finishes and install).
Step 5: Once the download completes, navigate to the Manage tab -> System -> Advanced.
Step 6: Select Storage and then scroll down to Downloads (some have noted that a reboot of the OUYA may be required after your first download to have this section appear).
Step 7: There will be a list of all the downloads, select the XBMC download and click install.
Step 8: ...and you're done! XBMC will be under the Make tab.