In case you haven't heard of it yet, the Tenebrae Project has been hax0ring the Quake source code in order to add many of the features expected to be in Doom 3. However, I'm not quite sure how similar the lighting methods will be, because John Carmack has repeatedly emphasized the importance of hardware pixel shaders in his scheme, but they don't appear to be used in Tenebrae at all (I'm able to run it on my GeForce 2 fairly well). Well, it's pretty interesting regardless. They also have a link to a Quake E1M1 texture replacement project, which reminds me a lot of FreeDoom. Heh.