Is it possible to edit the keybindings in Super Meat Boy?

It is possible to edit the control mapping, although not in-game. In order to do this you need to edit the file buttonmap.cfg. If the game is installed on Steam, it should be located under:

Program File > Steam > steamapps > common > super meat boy >buttonmap.cfg

The file will look like this:

keyboard
{
    up="up";
    down="down";
    left="left";
    right="right";
    jump="space";
    special="shift";
}

gamepad
{
    jump="1";
    special="3";
    useanalog="true";
}

Simply edit the corresponding line to change the key bindings. For example:

keyboard
{
    up="up";
    down="down";
    left="left";
    right="right";
    jump="z";
    special="x";
}

gamepad
{
    jump="1";
    special="3";
    useanalog="true";
}

For those on Mac OSX Steam this can be found at the following path. Remember right click and to use show package contents on the

$HOME/Library/Application Support/Steam/SteamApps/common/Super Meat Boy/SuperMeatBoy.app/Contents/Resources/buttonmap.cfg