Linux 3.5 has been released on 21 Jul 2012.
This release includes support for metadata checksums in ext4, userspace probes for performance profiling with tools like Systemtap or perf, a sandboxing mechanism that allows to filters syscalls, a new network queue management algorithm designed to fight bufferbloat, support for checkpointing and restoring TCP connections, support for TCP Early Retransmit (RFC 5827), support for Android-style opportunistic suspend, btrfs I/O failure statistics, and SCSI over Firewire and USB. Many small features and new drivers and fixes are also available.
Read More: http://kernelnewbies.org/Linux_3.5