SQL Server equivalent to functionality of Oracle RAC?
No, nothing in SQL Server can give you the same thing out of the box.

Currently, the only SQL Server technology that allows simultaneous writes at multiple nodes is Peer-to-Peer replication. Note that I did not to say "write scale-out," because it works in a way such that the entire system has the write capacity of only a single node. The introductory paragraph of that page is worded carefully to include the term "scale-out" without saying "write scale-out." Yay for marketing-speak.

From what I've read, Oracle RAC is the same in that respect. Functionally, the only thing that's missing from SQL Server in this configuration is a load-balancing solution, which is both an advantage (you can implement it any way you want) and a disadvantage (it's not in the box or supported by Microsoft) when comparing against competing products.

Conversely, Oracle RAC does not give you the same thing as SQL Server out of the box either. For example, RAC is recommended to be implemented with nodes within 100km of each other because of realtime network latency, whereas Peer-to-Peer replication has no such restriction. (I'm not saying one solution is better than the other: I'm just pointing out that they are different. The business should choose a solution that best fits their specific needs.)