No there isn't.
You can download Wii games on to the Wii via the Virtual console or Wiiware, but you have to pay for them.
To play wii games you need to buy them in stores.
It is Not the same but i have heard about dedicated web sites which games are Wii compatible for you use the pointer as mouse via the INTERNET Channel, not the same though.
And i have not searched one, sorry.