Tested and working: Spider mob spawn experience farm

After watching (and testing) multiple Mob spawner and experience farm how-tos on youtube, Dowsy's tutorial is a winner!

And my version, in a Multiplayer server, following Dowsy's instructions exactly;

The dungeon surrounding the spawner is 9x9 (dig 4 blocks out in all 4 directions) and 3 blocks high (one block on both top and bottom of spawner).

The project will require:

• 1 Spider mob spawner
• 1 Lever
• 1 Button (of any material)
• 6 Redstone torches
• 10 Sticky Pistons
• 12 Glass Panes
• 15 Glass
• 18 signs
• 20 Repeaters
• 22 Buckets of water (though you don't need that many actual Buckets)
• 63 Redstone

And a whole lot of digging!

I will note that, as Dowsy explains in his video, the spiders can hit you when you step down in the corner to get the loot but it's not serious if you make sure you keep your food level max.

The only downside that I can find to using Dowsy's method is that it takes a lot of Redstone and Sticky Pistons, which may not be available to many in Survival mode or in a Survival server, but otherwise, this is, by far, the best XP farm technique I've seen used!