Purchase keyword script?

I noticed a few sites have a purchase keyword type deal going on where the user can pay for a specific keyword on the page to appear in bold. I am interested in knowing more about this. Is there a script of some kind that offers this? Thanks.

 

Search for "tag cloud script". That's what it's called.

Here's one: http://www.wordcloudgenerator.com/

 

Thanks a lot. Aren't things like this against most search engine policies though? That is why I never bothered with it. However since I see so many sites using it now I wonder if it is OK.

 

Do you mean tag clouds are forbidden?

 

I don't believe tag clouds are forbidden
You can get a free copy from here

 

Thanks a lot for the link. Yes I thought that Google may not like users using a system like that.