Summer is over and autumn is here. Serotonin levels are dropping and people don't have the motivation to be outside as much anymore. So we play Minecraft instead. But walking is cumbersome, so we want minecarts. Remembering to carry one in your inventory or placing one on the tracks might be a bit much to ask for, and don't even get me started on bothering to press a button to make it go.
So lets make a fully automatic cart dispenser/accelerator-system.
4x2 wide and 3 deep.
Place 3 blocks, 2 redstone torches and a repeater on max delay.
Add 3 more blocks and a torch above the repeater.
Add a redstone torch and tracks like this. It can be a bit tricky to get the curved track to place itself like this, but try a couple of times and you'll get it right.
Place an empty minecart on the detector rail. It should start moving downhill by itself and then "bounce" up and go into the upper block like this.
Place a block on top of the torch in the lower left corner and place a dispenser beside it (pointing towards the powered rail). Cover up the hole; the two blocks to the right of the dispenser has to be placed above ground or the minecart will get stuck on them.
Add some more rails and place a mine cart on the powered rail, fill the dispenser and you are done. :)
Enter the cart and it will start moving and after a while a new minecart will be placed so you don't have to remember to carry one next time you want to take a ride.