Although we have been teased glimpses of future builds of Windows 10 and have peeped leaked builds, Microsoft's official build for 'Windows Insiders' is currently at build 10130. Today, due to special circumstances, Microsoft has released the ISOs for Windows 10 build 10130.
In the past, Microsoft has traditionally held off releasing ISOs for its 'Insiders' until the current build has been released for both fast and slow ring users. While fast ring users have been previewing build 10130, slow ring users have yet to experience the latest build due to some bugs that have yet to be ironed out. Interestingly, due to some fast ring users having issues upgrading to the latest build, Microsoft has made a special exception by releasing the ISOs for Windows 10 build 10130.
Windows 10 will arrive in the summer of 2015 and will be free to those that currently own a legitimate copy of Windows 7, 8 and 8.1. For those that have yet to do so, it is recommended to reserve your copy of Windows 10.