Since there's not as much "lounging by the pool-side" on Alaskan cruises, many folks find that Inside Passage cruises are "all about the excursions." I've known people who book the cheapest inside cabin they can get, just to save a few hundred to allow a bit more in the excursion budget. Also, a friend of mine makes a habit of "paying herself first" each month... $50 every paycheck isn't too huge a sum to put aside (for me, I cut my HBO and drop the speed of my internet access to save an extra $50 per month) and when it comes cruise time, a few hundred will be built up for excursions and fun stuff.
Yes, I'm in the business of providing excursions, so it's natural to hear me say just that. Having said so, however, there is plenty to do on the cheap in each port. In Ketchikan and Skagway, you can walk the entire "touristy" part of town and then some. Hit the Forest Service in Skagway... they've got a neat walking tour map and movie about the history of the town, etc. Ketchikan is very condensed and easy to access everything. If you want to get to the totem park and "native villiage" just hire a local cab and go for it.
In Juneau, the City and State Museums are both very accessible on foot (no more than a mile), as is the World Famous Red Dog Saloon (right downtown) and a number of other attractions. It used to be that all of the boat excursions left from Auke Bay and required a shuttle or expensive cab ride to get to. This year, however, look for a few charter boats to run sport fishing or whale watching excursions right downtown at Marine Park or the IVF next to the Mt. Robert's Tram. Also, there are powder blue school buses labeled "MGT" that will shuttle you to Mendenhall Glacier for $6 or $7 per person each way. (This IS NOT the City Bus... nor is it a bus "tour".) Once you're at the glacier, the Visitor Center charges a few bucks ($2 or $3) to enter, and it's well worth it as well...
If the budget allows you to eat OFF SHIP, stick to the street carts and local vendors, and stay out of most local restaurants. You can get a King Crab leg for a great price, as well as Halibut Tacos, BBQ, and all sorts of great eats for much better prices vs. the Restaurants. The one exception I might make in Juneau is Costa's Diner... less than 10 seats in the whole place, and no pricing on the "menu".... They'll ask you to write down what you want on a post-it note. If they have it, they'll make it for you. Portions are HUGE, and when you're done, you pay whatever you think it's worth into a huge money bucket and make your own change. Don't look anyone straight in the eyes, however, or you're likely to get sucked into a major social or political discussion that you really didn't bargain for in the first place... Great way to meet locals if you just want to sit and chat all day long though! ;-)
Hope my ramblings help... off to shovel snow out of my driveway again!
Happy Alaska Travels!
-Case