SMPlayer, a Qt front-end for mplayer, has reached version 15.9.0 recently, this being the first stable version to support mpv. There are various other new features as well, like support for 3D stereo filter, MPRIS v2 support, a new default theme and more.

VA-API is an open source library/API which enables hardware accelerated video processing. It uses the GPU to accelerate video processing in order to offload the CPU.

Supported hardware includes Intel HD Graphics and G45 chipsets and newer as well as AMD Radeon GPUs (there's also a Nvidia VDPAU backend for VA-API). You can find a list of supported hardware, drivers and video codecs HERE.

Here's an example: on my laptop (Ubuntu), the CPU usage is around 40-50% when watching an 1080p H.264 video using MPlayer without VA-API and around 2-5% when watching the same 1080p video using MPlayer with VA-API. You can see some screenshots below:

GNOME MPlayer 1.0.7 has been released recently, getting support for MPRIS v2 (e.g. Ubuntu Sound Menu integration), along with other enhancements.

GNOME MPlayer is a GTK2/GTK3 frontend for MPlayer which, besides playing audio and video files, it supports DVD and MKV chapters, cover art retrieval from Amazon.com for audio files and other useful features.

SMPlayer may have been dead for a while, but it seems very active now, with two releases in just one month. The latest SMPlayer 0.7.0 brings basic support for YouTube and MPlayer2 as well as other new features.

MPlayer2 is a fork of MPlayer that "contains significant further development and supports a number of features not available in other Unix players".

SMPlayer is a popular front-end for MPlayer and can play videos, DVDs and VCDs, featuring configurable subtitles, audio track switching, video equalizer, filters, playlist, audio and subtitles delay adjustment and much more.

After almost 2 years, a new SMPlayer version has been released: 0.6.10. The new version only brings some minor new features like:

Xt7-Player is a graphical user interface for Mplayer with a huge list of features, "while trying to keep usability in mind". Among the most important features are YouTube and Shoutcast integration, dvbt, library and playlist management, local and global hotkeys, "stackable" Audio and video filters managed via drag'n drop, audio and video equalizers and lots more.