<select name="whatever" onclick="java script: fixForm(this); this.form.submit();">
<option value="http://foo.com;frame_a">Site A</option>
<option value="http://blah.com;frame_a">Site B</option>
<option value="http://whatever.com;frame_c">Site C</option>
Substitue/extend frame_X and URLs and titles as appropriate, obviously.
It doesn't meet accessibility requirements, so personally I would also add a button, but it's up to you.
EDIT: IPB foobared up my code box for security reasons so as to put a space between 'java' and 'script'. Should be a single word.
Edited by Chris Graham, 14 July 2006 - 01:47 PM.