Well the usual options are always the same for exterior stuff: do nothing and allow it to weather to grey, a penetrating finish (an oil or one of the oil finishes), paint, marine varnish for the full-on encased-in-yellow-candy look or one of the coloured varnishes that most use on their front doors and window frames if they're not painting.
Finish selection can be made simpler by going through a simple checklist. Start with what do you want it to look like? Then what level of protection is required, the application method you'd like, what maintenance schedule you'll accept and last but not least what you can afford and/or get easily.
Go through that and the choice can be very easy, often you're left with a single contender.
