RoaringCore allows you to install Lion beta 1 on any unsupported Intel Mac, even after the beta 1 installer expired. It was released in Summer of 2011. Lion Developer Preview 1 could be hacked to run on Core Duo and Solo processors by installing it with a newer machine, then modifying some files, and swapping the HD to the older machine.
I did this. Unfortunately, Apple beta installers expire, so it is no longer possible to do a clean install. I took my installed copy, cleaned off all my content, and created a .sparseimage backup of it to distribute. I don’t recommend only having Roaring Core on your machine. You don’t get iCloud support, or iTunes syncing with 2011 and 2012 devices. But you do get Mission Control, LaunchPad, Fullscreen support, new gestures, and numerous other Lion features. A big thanks to http://longhurstconsulting.com/ for helping us with getting this to work.
File name: Roaringcore-Beta2.zip
File size: 3.41GB
Check out this video on how to install: