QGIS 2.2 is now available for Windows through OSGeo4W installer. Packages for other systems are being prepared by the package maintainers.
The Windows packages are currently marked experimental, so you have to use the advanced install in OSGeo4W and check the ‘Exp’ radio button on the top to install them.
Please test and report problems, so that I can soon promote them to ‘curr’ent.
Once that has happend, I’ll proceed with turning them into standalone