When we were in Flam some years ago the excursion we did was the Flam Railway which was quite good. However, looking at the time you dock and leave I doubt you could do this. I can't honestly remember much about the town itself, some of the stops on our cruise were literally one-street towns! Still, it is always nice to get off the boat and go for a stroll, even at such an ungodly hour!

the railway is the main option.

http://www.flaamsbana.no/eng/

Book in advance you have to get the first train.
If the ship is offering the railway tour then the railway may be sold out llready

For a few hours there are some walks and a samll museum.

http://www.flamsbana-museet.no/default.asp?sprak=3

http://www.visitflam.com/default.asp

Little tractor train gives your an hours tour of Flam and surrounding area pretty good value for money but only starts running at 10.a.m.

Train Museum entered through the gift shop very interesting and free.

Thanks for the info and the links.

We would have liked to do a return trip on the railway but time is a little bit tight for a d-i-y trip if there are any delays. The ship offers two different excursions on the railway but they both involve one-way journeys by train followed by coach trips ending at Gudvangen.

The cruise from Flam to Gudvangen is the only part of the cruise that is actually within a Fjord in the day-time so we don't want to miss it.

Having done the Flaam railway on a full-day stop, I strongly agree it is not really feasible to DIY on a short stop. Friends of ours also did this, and the train engine seized meaning they had to reverse (in controlled free-wheel mode) and be diverted into a siding for a replacement engine to be fitted on the train!!

Flaam itself is tiny, so wouldn't rush out for 8.00am, and you will walk around and see it in 30 minutes. You can walk round the head of the fjord alongside the water on the opposite side from berthing for a couple of miles which is pleasant if the weather is dry.