A lotta arcade games get played on the NewNet live stream. If you wanna join in the fun and need help with MAME, click the MA Ball above and come and see me (Hierophant) and the rest of the guys over at MameAddicts (MA).
To give some sense of direction for newbies, here are a few fundamentals:
The vid that started it all, "How to Install MAME" by the head MameAddict, Chris (aka Incito).
My MAME FAQs.
The all-important Online MAME forum where my Open Kaillera P2P tutorial originated (for MA members only). P2P is the best way to play arcade games with Atarix on the stream.