In reply to Russell Lovett:
Sam gorge is good, but make a really early start because it gets crowded, people walk too slowly and it can be difficult to overtake in places.
Best to get the bus from Chania to the start, otherwise you've got the problem of getting back to it at the end of the day - you go out by boat, then bus back to Chania. The decent of the gorge was about 3 1/2 hours, but we were held up by slower parties in places.
IMHO Imbros Gorge is even more spectacular and a lot less crowded. Very narrow canyon walls in places. You should be able to go down and back up in about 4 to 5 hours.
The gorge from Katohori to Stilos is also well worth doing with some interesting huge boulders to negotiate in the gorge itself. We took about 6 hours down and back up, but it was an exeedingly hot day.
The ascent of Gingilos(2080m) from Xiloska (same start as Samaria Gorge) is fantastic and quite exposed in places with great views down into the Samaria Gorge from the summit (which is about 10 mins on scrambling over boulders from the top of the path). About 5 hours.
Take loads and loads of water, there isn't any en route and we were drinking between 3 and 4 litres a day each in the heat.
If you visit Chania take time to visit the British War Cemetery at Suda Bay
http://www.cwgc.org/find-a-cemetery/cemetery/69004/Suda%20Bay%20War%20Cemet...
It's a really beautiful and peaceful, but poignant spot
Enjoy!
Post edited at 18:12