Harmonix has opened beta registrations for the Rock Band Network, a service that allows independent labels and bands to publish songs as paid downloadable content for Rock Band and Rock Band 2. For now, it's Xbox 360 only, with plans to launch on PS3 eventually. Bands can "suggest" a price point of either US$1, $2 or $3, and take home a 30% revenue share.
Creating songs for Rock Band Network
In terms of hardware and software, you'll need an Xbox 360, the Rock Band 2 game and instruments, a copy of music creation software Reaper, an Xbox Live Gold membership, and an XNA Premium membership.
Bands will also need the "stems" of their recordings, with vocals, drums, guitars and bass separated into their own files. They may also need to make a radio edit of the song, removing any profanities in order to reach Rock Band's T for Teen rating. Cover songs, or using samples, are strict no-nos.
They'll then need to create the note charts for the game using Reaper and a custom add-on designed to make the process much easier. I'd say a majority of bands out there have at least one member (or one close friend) who is familiar with music software like Pro Tools or Logic Studio and should be more than capable of doing this step, although the creation of a separate note chart for Easy, Medium, Hard and Expert modes will no doubt be a lengthy process.
There are also many companies who can help bands and labels get their songs in Rock Band, and the list of those companies is available at the Rock Band forums.
You can read about the song creation process in far more detail at creators.rockband.com.
With 60 million downloadable songs having been purchased for Rock Band, and Rock Band games and instruments still falling in price, the opportunity for bands and labels previously unrepresented by "official" downloadable content (and on-disc track lists) to get their music into the game has great potential as an additional revenue stream and promotional vehicle.
Unfortunately it appears that the time, cost and effort involved with doing so is so great that it's only the upper echelon of independents that will be able to participate. According to the Wall Street Journal, the well-known independent record label Sub Pop only plans to release 25 songs onto the Rock Band Network - all by the most commercially successful artists on their lineup. Tony Kiewel, head of A&R at Sub Pop says "At $3 apiece nobody's looking to 'Rock Band' as a discovery tool. [...] That's not going to happen."
Hopefully there will be a few labor-of-love projects from small-time bands that reach commercial success and propel the band to new levels of fame, with their stories becoming the Rock Band equivalent to the Apple App Store success stories (like iFart's $10,000/day revenue) and encouraging more bands and labels to get on board. A more generous revenue share wouldn't help either - especially if bands have to share it with a label.