<g:select name="confer" from="${orig}" optionKey="id" value="ola" />
<g:link controller="conferenceUser" action="addFavourite" params="[confer: confer]">Some text</g:link>
How can I get current selection from selectBox to pass in the params of g:link?
The g:link params are set when the page has been rendered. You will need some javascript which reacts on the select event of the select box. Checkout the jQuery Change method at http://api.jquery.com/change/ and look at Change URL parameters on how to manipulate the url query params.
Another way could be to intercept the click event and fetch the current value of the select element and then proceed.