In reply to maisie:
Im doing the Salkentay treck in September - ill let you know how we get on with the company we are with. You can still do this on your own at the moment but I think they are looking to change this soon.
If you want to do the Inca trail - book asap we looked at booking in March this year for September this year and it was fully booked from March.
I agree with neil9216 - from what we can see you will be starting with 400 people on the same day - all following each other.
Ive been reading the book 'turn right at Machu Picchu' - worth a read and from this it looks like that other less well known trecks north west from MP would take you into even less visited areas.
If you do want to go with a trecking company and want to book in advance most want you there 3 days before the start so you can acclimatise and they ask you to get attend a breifing 2/3 days before to make sure this happens - thought you may want to know so you can plan for it.
Drop me a line if you want to get any more info.