I don’t know if anyone’s submitted any combos for infinite mana, but i have found one which gives infinite colourless. This combo is very much playing the long game because of mana cost to set up, but the pay off if great. You’ll need three cards, Karn, Silver Golem (Vintage Masters), Thran Dynamo (Archenemy), and Volatic Construct (Darksteel).  To start this combo, with all cards out in play, you tap Thran Dynamo to get three mana, you use Karn’s 1 mana ability to turn Thran Dynamo into an artifact creature. then use the 2 remaining mana to use Voltaic Constructs 2 mana ability to untap Thran Dynamo (which is now an artifact creature). Rinse and repeat tapping Thran Dynamo, and paying 2 mana to untap it, and ramp up to the amount of mana you want to use.

From @mancalledintrepid

Eight mana to get a 5/5 may seem like a lot, but this is actually part of an arbitrarily large combo for getting 5/5 Trample Beasts.