If you've signed up for the Yosemite beta program, you now have access to the beta of Apple's iPhoto replacement, Photos. It's available in the Mac App Store right now.
The new Photos app is packed into the Yosemite 10.10.3 public beta pre-release. With it, you can access to your iCloud Photo Library where you can browse your photos and edit them with simple controls.
You'll need to be a part of the beta program to get it, but if you haven't signed up for Apple's beta program, you can do so here. Once you're signed up, you can download the update from the App Store. As always, this is a beta, so don't expect too much from it.