Future, meet your past. The fine lads at xda-developers forums have ported the Android 2.1 ROM -- you know, the updated OS from Nexus One that everyone's been talking about lately -- all the way to the original G1. Right now it's being dubbed version 0.9999 since it's still lacking A2SD, CompCache, and SWAP... and if you're feeling confused by the terminology, it might be best to not try this at home just yet. Creator Teh Dust has also removed a few things for the sake of making it more lightweight, including Car Home, Live Boot, and high resolution wallpapers / apps that don't jive with the G1 anyway. Willing, curious, and wanting to impress your Droid-carrying friends? File's hiding in plain sight, waiting for you.
Update: Quoth the raven, 'twas a hoax and nothing more.