The Minecraft server has been updated to the latest CraftBukkit beta build supporting Minecraft 1.7.2 (changelog) and will remain so until newer versions of Bukkit are released. This post will be updated accordingly.
See the wiki for changes and improvements in this version. If you haven't played since Minecraft 1.4, 1.5, or 1.6 you should review the changes since version 1.5 (the "Redstone Update") and version 1.6 (the "Horse Update"). Dozens of new features and blocks have been added including hay bales, charcoal, and carpet. Horses, donkeys, and mules have been added to the list of mobs in Minecraft 1.6 and you can now create a "lead" (basically a leash) to force mobs to follow you, domesticate additional animals, and ride horses or utilize pack mules for your gear.
Moreover, 1.7 now includes substantial changes to the terrain generator, including new biomes and improvements to existing biomes. There are now various "rare" biomes that spawn infrequently that have certain unique features specific to that biome (e.g. flower forests).
You'll need to download the latest launcher to be able to play Minecraft 1.7 (Windows binary; other platforms need the .jar). If you've played Minecraft since 1.6, you have the new launcher. If not, then you need to download the latest version.
If you encounter problems while playing on the server, disconnections, or anything unexpected, please post a new thread describing your problem.