No hablo español... and I don't use Eclipse (as it seems you're inquiring about a Portlet plugin for Eclipse).
You'll have more luck getting an answer writing in English... sorry about that. :(
I'll try to write in English.
I want to create a portal and i need a plugin or java libraries to develop it, for example javax.portlet.*
do you know were i can download it?
An implementation of the API is included with JBoss Portal. You can also download it from the JSR-168 page: http://jcp.org/aboutJava/communityprocess/final/jsr168/index.html
Reading the specification is a good idea before starting developing portlets :)