The best filter colour for white light solar observation (eg. with Baader film) of surface details (granulation, etc.), is supposed to be dark green. Baader themselves make a dark green 'Solar Continuum Filter', which they claim is even better, although I've read comments for and against. There's a detailed description here:
http://www.aoe.com.au/solarobserving.html
In the text, Baader claim that, "Details like flares at the sun's rim or details within sunspots become clearer and easier to see", which sounds promising. Unfortunately, I think I've read that the advantages - if any - are for photography rather than visual observation. If you're a looker rather a shooter, I believe Craig's comment that white light viewing won't show prominences is correct, unfortunately.
My own preference is Hydrogen Alpha viewing with a Coronado PST - even at the present solar minimum, interesting surface activity is frequently visible and prominences are commonplace. PST's aren't a cheap instrument, but Sol is the only star in the sky that any of us will ever see up close and personal and the view is amazing!
