Apple has launched OS X 10.10.5 in beta for developers. It can be downloaded from Apple's Mac Developer Resource Center right now. Developers with the previous beta build of OS X Yosemite installed should also be able to download this new version from the Updates section of the Mac App Store right now.
The latest release of Yosemite, OS X 10.10.4, launched publicly two weeks ago. It featured a number of improvements, including networking fixes, Migration Assistant tune-ups, and more.