While an alpha version of Firefox 3.6 is now available from this page, a new theme for Firefox, based on the first mockups interfaces of Firefox 3.7 and Firefox 4.0 unveiled recently on Mozilla Wiki, was published: it's Strata40.
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I'll definitely be trying this once I've got my laptop back - don't think it'll last though
I've used plugins and such to get me to look like 3.6, askvg.com had the stuff. I'll have to try this and compare.