Can anyone recommend an offline mapping application for Mac (something similar to Google Maps, but that works when not connected to the internet)? Ten years ago, Microsoft Streets and Trips worked well for Windows, but I'm looking for something similar now for Mac.
Planito seems to be a good app for offline map viewing. It allows you to cache and view many different maps:
Planito does cost $4.99, but there is a trial available.
RouteBuddy is a dedicated off-line mapping tool that seems to fit your needs. It's not cheap ($60 plus taxes) but it is very impressive.
I downloaded the trial version which comes pre-loaded with vector street maps of Santa Fe, NM and a topographic map of Yosemite National Park. You can (without internet) easily search addresses, navigate, set waypoints, etc. and their website also lists several other features such as route statistics/elevation data/GPS support, among others, which I presume is available only in the full version.
Since this is an offline mapping tool, you'll have to download the maps and check everything before your trip. Although it feels a bit slow to zoom in the first time, it's faster the second time onwards, once the data has been cached.
Below are a couple of screenshots of Santa Fe, NM and Yosemite as seen in the app.
...has listed a large collection of software which uses it's data for Mac/PC or mobile devices.
This is a terrible cop-out of an answer, but the best solution I've found so far is to run Microsoft Streets and Trips under Windows on my Mac.
I tried Garmin BaseCamp with my GPS attached to the computer via USB cable. The software was slow, clunky, and unwieldy, compounded by the fact that I had a large item hanging off of my computer. So amazingly and unfortunately, the best mapping software I've been able to run on my Mac involved booting into Windows.
This might be working for you. It's not been updated in a year, though, and requires a tiny bit of extra work upfront to get it up and running. Offline support is advertised.
Then there's also http://www.mifki.com/planito/ which costs $4.99 but has a free demo. It's not open source.