i've used these /commands
but i am not sure which are donors+ only
/fly = donor for sure (sets fly mode on/off)
/sethome [name the area] (up to 20 unique locations)
/home [preset location] (teleports you back to the home of your choice)
/home (shows list of preset homes)
/top (teleport to surface)
/back (return to previous location, even if in different world)
/worth (displays sell price of item in hand)
/sell all (sells everything in your inventory, be careful!)
/sell hand (sells item in hand and all of that same item currently in your inventory)
/pay [other player] [amount] (send selected player certain amount of in game money)
/balance (shows current in game money balance)
/balancetop (shows list of richest players and their balances in descending order)
/warp (brings up a list of locations anyone can teleport to)
/warp [location] (warps you to the location)
/tp [other player] (teleport to player, or sends request to player depending on privileges)
/tpaccept (accept a player's request to /tp to you)
/repair (repairs item in hand without level cost or anvil)
/feed (fill hunger bar without using food items)
/unlock {then punch block} (unlocks chests, dispensers, etc...)
/lock {then punch block} (locks chests, dispensers, etc...)
/chopper on {then punch block} (allows hoppers to work on chests, dispensers, etc...)
/chopper off {then punch block} (disables hoppers from working on chests, dispensers, etc...)
i'm sure i'm missing some. so i'll edit this post if i find/remember any and add them.
i've yet to try:
/send [other player] (sends item in hand to selected player's inventory)