Update: Snapshot 13w38c has been released to fix numerous graphical issues, crashes and item frame issues.

--Features:
-(Old feature): Pressing F4 stops all shader effects.
-Notable bug: Arrows shot by bows act strange.
-Notable bug: Arrow sound effect plays double when skeleton shoots, and also when skeleton -is hit by an arrow.
-Notable bug: Tree Leaves seem to be using the "Fast" color, since there are much brighter then before. (Even if you're on "Fancy" settings)
--Fixed bugs
-MC-3973 - Silk Touch, pre-lit Redstone Lamps
-MC-31876 - Hopper: java.lang.NullPointerException
-MC-31880 - Hopper: java.lang.NullPointerException
-MC-31883 - Killing mobs sometimes drop "tile.air.name"
-MC-31888 - Hopper: java.lang.NullPointerException
-MC-31892 - Nether entering crash.
-MC-31906 - Hopper: java.lang.NullPointerException

The client is available in your launcher, and the server links are below.

Download:
Cross-Platform jar: https://s3.amazonaws.com/Minecraft.Download/versions/13w38c/minecraft_server.13w38c.jar

Windows EXE: https://s3.amazonaws.com/Minecraft.Download/versions/13w38c/minecraft_server.13w38c.exe