We're currently trialling Atlassian Crucible in order to facilitate code reviews. If you want to participate or upload a patch for review, go to http://crucible.openclonk.org/ and register an account.
Be however advised that Crucible by default will send you an e-mail notification for every single thing that happens on reviews you're participating in (whether as reviewer or author), and I can't set more sane defaults, so you might want to go to your user settings and set the notifications to "Batch" (which means you'll get an e-mail every 30 minutes if something happened) or "No". Check Atlassian's knowledge base for more details.