I have done quite a bit of this. Here's a review:
1. AML. Pro organization. Among the more expensive, but competitivly priced among commercial freight carriers. Part of Lynden transport so any trucking needs can be rolled into one quote.
2. Samson Tug and Barge. Same as above, not as much capacity over land though.
3. AMHS: The ferry. If you can find a sailing that works for you, this is the way to go. It's subsidized. You'll end up getting on and off a few times, but you are basically looking for sailing to Whittier. You can also take the ferry to Haines Jct. and tow the rest of the way, but I wouldn't do that. This could be your most inexpensive option. Plus a nice trip. Plan to spend some nights in ports like Juneau. If you bring a boat and don't have a tow vehicle too you can arrange to have your boat hauled off the ferry and put back on by someone in each town ahead of time. It costs about $100 or so to have this service performed at a port. If there is no vendor in a town where you need to switch boats that you can hire the ferry will usually do this for you, they just won't if there is someone running a business: they are the State, so they can't compete with private business.
4. UShip. Uship is AWESOME! I have had nothing but great experiences with multiple carriers. I've gotten great service, usually somewhere around 20% of the quoted cost from a freight carrier. Not 20% less, 20% OF. So a carrier quotes me $10k, and Uship comes in around $2k. It rules. The site has reviews. People who are well reviewed are reliable!
5. Canneries. In April there are a LOT of tenders that travel from the PNW to Alaska to tender in commercial salmon fisheries, then another smaller run of tenders coming for pink salmon in mid June. If you have any contacts in the commercial fishing world, use them to find a tender coming north. These boats are usually empty and the captain will take a small boat as a deck load usually for beer money. They are usually pretty happy to have a good small boat on deck in case of emergency. You can try calling canneries directly but you will do better if you work through someone who fishes for them. Google can help you figure out which processors to ask, however don't miss Trident or Ocean Beauty Seafoods. They're the big ones. Lots of others though.
6. Craigslist. There are people on there who advertise that they will tow your boat to AK. Never tried it, never would, but it's an option! Risky though.