Is there a plugin to use some external tool operations like "sed" or "grep" with a text selection per shortcut ?
i want to use sed for transforming some parts of code with a predifined shortcut.
AFAIK there is no such a plugin. However, there is an existing infrastructure for calling external commands from the IDE. It's even possible to use selected text as an input, the only remaining thing is to change the selection by external command output. I'd suggest you to have a look into this plugin which reliefs custom actions construction and already provides useful bundings to editor/document etc.
if you want something little bit different
with this plugin http://plugins.jetbrains.com/plugin/?idea&pluginId=7173
you can create an action with shortcut, which will execute your own groovy script on selected text and transform it. There is already a template for that, so it is really easy,