I wonder if exists a widgets to run these scripts in opera.
Something like greasemonkey exstension.

http://en.wikipedia.org/wiki/Greasemonkey#Opera

Yes there is: UserJS Manager.

This might be of some help.

@avg
I think you made a typo in your link

@kantor & anyone who finds this thread while searching
Opera has userscripts built in, no need for an extension (jerone's link above is a very useful extension for making userscripting more convenient, but isn't necessary). Opera's own website has info on greasemonkey support.