This answer is discontinued. Please move to here
Xposed for Oreo is unavailable by far because O is ... too new
Update 1: Official Xposed v88.1 for SDK 25 (Android 7.1.x) is available as of October 10, 2017
Original Answer:
An unofficial build of Xposed Framework is available from XDA. I have tested it with my OnePlus 5 and it worked perfectly.
The XDA newsfeed article is here and the thread is above.
Important Notice
If you are using your stock ROM, make sure your/data
partition is decrypted. If it's encrypted, you may have to format it. Be sure to back up your data carefully before proceeding. Also you should flash a "DM Verify and Forced Encryption Disabler" package.