Since minecraft 1.3.1 dispensers can dispense minecarts. Mojang didn't think this all the way trough and because of that you cannot pick the minecarts back up with the dispenser.... UNTIL NOW!
This plugin does only one thing, but it does it very well. As soon as a minecart hits a dispenser it gets picked up by the dispenser.
This couldn't be more easy. Just download the .Jar file and place it in your plugins folder. Reload or reboot your server and the plugin is loaded. Now put some minetrack against a dispenser, Put a minecart on it and watch it go *POEF*!
Of course you can! Please watch this short youtube video: http://www.youtube.com/watch?v=-b5BqSepG3Q