Agree MX Mariner is great for the US. I wish they'd offer a way to buy Canadian charts.
Applications and chartplotters including AC data is a great development.
But what I've seen leaves a lot to be desired in terms of actually using that data.
Underway, or planning the night before, we're looking for something specific. An overnight anchorage in a quiet location. A reasonably-priced slip in town. A fuel dock that won't rob me blind.
What do we have? Dozens of little icons that we have to click on, one by one, then click to open the AC data, then click to open the details, then click to open the prices, then click to open the reviews. Only to find out, most of the time, that it's only a day anchorage, or the marina doesn't take transients, or for whatever reason it's not what we're looking for.
The real trick would be to be able to select just the places that have what we're looking for.
The AC website is probably the closest thing there is to the ideal interface. But even that hasn't really had any new search or usability features in a long time. And between Flash and the small form factor, it's not appropriate for phones and tablets.