Hi, I am taking two car ferries and would like to know how far in advance I should book them. We will be traveling the first week of August. I would appreciate any input.

Do you know how to book? I am wondering the same question (planning Kaupanger-Gudvangen)

Moonininjuly, that route is Fjord1 ferries. Just go to Fjord1.no website. I don't know how far in advance to book.

I forgot to say which ferries I am taking. One is from Vangnes to Dravik, and the other Bodo to Moskenes.

Vangsnes-Dragsvik is a road ferry and can't be booked - join the queue (not usually a problem).
http://www.fjord1.no/eng/ferry
Kaupanger-Gudvangen is a tourist route and can be booked - http://www.fjord1.no/eng/tourist-services
Bodø-Moskenes you should book in advance (assuming you are travelling with a car). http://www.torghatten-nord.no/english/default.aspx

I tried to book torghatten ferry, but it would not accept my Visa Card from US, I may try by phone.

Dyoll's info is spot on. We used the ferries a number of times (all road ferries) on a trip a few years ago and never had a problem getting on the next ferry to arrive (then again, we went in October).

In any case, they were all nice, ran generally on time, and were a nice way to experience Norway (even on the road ferries). We tried to time them to have a picnic lunch on board (some even little snack bars). They were also a good way to meet a few Norwegians and get a few local suggestions.