I'm still new to Minecraft, but after reading alot of threads in here, I think these three Idea will cater for ALOT of people.
Firstly, The Dispenser, there are Threads about the dispenser being able to receive goods, If they land on top of (or close enough to) the Dispenser, I'm not stating a new Idea so much as pre-qualifying this to make more sense of later concepts.
Not only should the dispenser dispense items, but if it receives the pre-defined items, It should spit out a crafted recipe. i.e. if it receives 3 stone and two wood, and you have put them in the standard 'stone pick-axe' pattern it will then dispense a stone pick-axe.
Furthermore, the Dispenser if placed in a Minecart, will still work, provided the minecart sits next to live redstone.
New Concept: The Recogniser. You place 2 Items in a recogniser, if it recieves either of these two items, it spits them out again, Left for item 1, right for item two, ahead for anything else.
This last item could be done in multiple ways: The Redstone Bot. Made from Iron, Diamond, Redstone and Moonstone? The concept is that an item, singular could be transported along a path, be it a small spirit that travels along a redstone path if the path is 'on' grabs items from one end and takes them to the other (and grabs 'other' items from that end and returns to the start) or returns empty handed if no item exists. OR it would be a cart addition to preform the same task.
If you don't already see the connection.. Redstone is as electrical circuits, enabling alot of interesting switches, but now items can be included in the switching process.
Lets say you set up a redstone Spirit, near your tunnel, he takes back everything you drop near him to the nearby recogniser, if its anything else it goes in the Dispenser Cart, if its full it drop the extra item on the next dispenser which is set to pop out a stick into the nearby furnace, which moves around a track and hits a trigger, causing the dispenser cart to leave. It travels down to your base, and when it arrives next to redstone it powers up and spits all its items to a series of recognisers which sort through all the stone you sent back. The recognisers take stone/metal and wood sticks and the Dispenser workbench spits out some axes. The nearby cart with dispenser picks it up, and when full sends its back to where the player is mining.
The Player essentially loads up the cart with all the stone, soil, gravel and ore, and periodically gets back 9 fresh tools which spit out next to the cart point. When the area is cleared and cleaned up, the player doesn't need to re-set all his carts, but just sorts out some redstone lines to the next spot.
If you want some more ideas.. heres where this thought conjured was up...
Seems like a hell of a lot of work for something that's very, very trivial and easy. It also seems pretty specific, as there are few situations where I would actually want to use these things. It's not hard to carry around a workbench. A specialized dispenser is superfluous. If you want, I can provide my complaints in more detail, but as of now, I'm going to put foward a rating of : Too Complex and Unesecary.