I just got my puppy 2 weeks ago, so I'm fresh from the crate training experience. I did take time off to be with the puppy, but I don't think it's necessary and the only option. Here is what I did:
From day one, puppy slept in the crate. I know how tempting it is to let the poor thing snuggle with you, because he wants to so bad, but you need to be tough. In the end he will be happier.
Also, the crate can't be too big. Don't feel like you're being mean, but he should have just enough room to stand up and turn around - if it's too big he will mess in one corner and sleep in the other. If it is small enough it will encourage him not to mess in his bed, because his Dog-mom has been teaching him since birth it's not allowed to mess where you sleep/eat. If it is too big use something as a divider that isn't porous, in case of accidents.
Another bonus to crating him at night is that he will not associate being in the crate ONLY with you leaving him. If you can have the crate by your bed, and if he starts to really whine, give it a rap on the top and say "Quiet!" or whatever you want. It'll become a command eventually (My puppy never cries unless he needs to go pee, and it's only been a couple weeks).
Never let him out of the cage if he is crying, because that will teaching him that he can whine and get out. Only let him out if he is calm and quiet.
If you haven't already, start doing crate practices during the day. Leave the crate open in the area you are, and throw in some treats or kibble a few times throughout the day - he will sniff them out and begin to learn the crate is a nice place where nice things sometimes happen. Positive reinforcement.
Sit down with him beside the crate, and lure him in with some treats. Close the door. Sit there and talk to him, nice and quietly, put your fingers through the grate and let him know you are close. When he is quiet, give him a treat (be quick, cause the quiet moments don't always last long), and let him out once he is quiet. Do this for a few minutes at a time, bring him out, cuddle, put him back. You can add your command word "Go to your castle" or something, each time you set him inside.
On your days off, if you are cleaning or something, lock him in his crate somewhere where he can see you - again, so he doesn't associate the crate with you going away. He will whine, tell him to be quiet, and ignore him if he gets whiny. Go about your business.
It's all about patience, positive reinforcement, and being tough. I would suggest getting a KONG. Everyone here suggested it to me, and I finally did it, and it does keep the puppy busy! They have them at any pet store, and they are not too expensive.
P.S. What I do when I am leaving him by himself... I turn on the TV. The people voices comfort him, and he doesn't feel so alone. I also leave the bedroom door open, because if it is closed I think he might feel isolated and even more alone.