If you want to learn about how redstone works this is the video to do it.
A space themed adventure and puzzle map, Deep Space Turtle Chase is epic! You need to do a little more to get it installed and running.
Escape the puzzle master and the dungeon. A fun puzzle map with some mind bending and parkour.
With 9 challenging and original puzzles, and they are, Puzzlecraft will keep you mind in shape quite nicely.
Team Fortress 2 PvP map come to you from SethBling and requires no mods. The best part is that is uses command blocks.
Handy for timed parkour puzzles. The Pulse extender.
Great video on pulse limiters. It had more than one design too.
VMware for mac is nice when you need Windows from something like this app that lets you build Minecraft music for adventure maps. It build the Note Blocks for you but you will need download MCEdit to drop it in form how I read it.
This video is great for seeing why you should use MCEdit to make your terrains.
All the different types of redstone circuits can be found on the wiki site for Minecraft.