Raskin
It’s going to be a one-item list, because Raskin is the only application I use other than the Finder to navigate the filesystem on my MacBook Pro. Strictly speaking, it’s not a Finder alternative — not for me, at least — but a nice Finder augmentation tool.
I’ve been using it since its beta version back in 2010, and despite a few performance problems, it’s the only tool in the ‘Finder alternatives’ category that has remained with me over time.
Raskin is a zoomable user interface to view and manage practically everything on your Mac within a sort of giant desktop surface. Its name is an obvious reference to Jef Raskin and a homage to his research on the ZUI (Zooming User Interface). You can read a detailed overview of Raskin’s features at Raskin’s website. What I find most useful is the fact that I can see at a glance the entire contents even of huge folders and subfolders, because with Raskin you can browse and move through your stuff as if it were all laid out on a giant desk. You can pan and zoom anywhere, and the feeling is somewhat similar to using Google Earth to make virtual trips around the world. Or to having a telescopic Quick Look feature.
You can use Raskin to move from an application to another, and if you focus and keep zooming in on a particular document, you actually open it in the designated application; but I mostly use Raskin as a photo browser (with Light Table View), and as a search tool. Thanks to Raskin, in fact, on more than one occasion I’ve been able to find certain files (PDFs and images, especially) that I had misplaced or whose location I’d simply forgotten.
In my opinion and experience, Raskin is quite useful to find items whose filename you can’t even recall, or whose filename is so generic you can’t possibly remember what it’s about. This is particularly the case of sizeable folders containing dumps of iPhone photos: if you haven’t tagged them in any way, it’s not easy to locate that photo you took outside the Louvre in a folder with 1,600 image files all with names like IMG_3389.jpg, IMG_3390.jpg or DSCN4783.jpg, DSCN4784.jpg, etc. With Raskin you just zoom in on the target folder and scroll until you see the photo you’re looking for. This technique also helps when you want to create a themed photo gallery with criteria like “All the photos prominently featuring a certain colour (red, yellow, etc.)” or “All the photos with type-related elements”, and so on.
The only problems I’ve experienced with Raskin have all been related to performance and responsiveness. As you can very well imagine, to be able to show you so much all at once, Raskin has to create previews, calculate item sizes, things like these. In the past, when I was using it less frequently, things could get frustrating because every time I opened Raskin, it had to update all the information that had changed since the last time I used it. That task was usually very resource-intensive, and trying to do anything in the application during the ‘rebuilding’ stage resulted in spinning beach balls and general unresponsiveness (and sometimes even the unexpected quit). But these problems have been constantly addressed by the developers over time, and Raskin has got snappier. You still need a powerful Mac to have a smooth user experience, though. On my 15-inch MacBook Pro (mid-2009, 2.66 GHz Core 2 Duo, 8 GB RAM) it feels ‘just right’ with the occasional hiccup. Your mileage may vary.
You can purchase Raskin on the Mac App Store or directly from the Raskin Store. At $24.99 / €19.99 for a single user licence, it’s hardly the impulse purchase, but you can download a free trial version from Raskin’s website and see if it’s the tool for you.