You want to have a look at the 8.0 version? It's not released yet, but you can download it at the download page and indeed use trunk (dev). There should be a nightly build there, but I think recently people slept at night, as the latest version is of April 17th.

You could also use github and build it yourself. That one is most actual. I am curious whether people did that recently and whether it contains a lot of changes compared to April 17th version. E.g. that one is still "OpenERP" branded instead of Odoo.

As far as I know, 8.0 will be released in the beginning of July. So probably then the nightly builds will be updated again and it will move from dev to a proper 8.0.