With the MacBook Pro, Apple discarded the old PC Card slot in favor of ExpressCard/34, a more compact expansion slot that offers greater transfer speeds and an increasing array of uses. The ExpressCard format has a couple of advantages over the old PC Card format.
First, it's narrower: ExpressCard/34 cards are 34mm wide, compared with the 54mm PC Cards. (ExpressCard/54 cards do exist, but they don't fit in the MacBook Pro.) ExpressCards also require less power--1.5 volts, compared with 3.3 volts for the PC Card. But their biggest advantage is speed. An ExpressCard passes data to the system at up to 2.5 Gbps; PC Cards supported speeds of only 1.06 Gbps.
Here is just a sampling of the ExpressCards available. It's by no means encyclopedic, but it should give you an idea of how you can expand your laptop's powers.
After using (and frequently leaving behind) USB memory card readers and cables to transfer digital photos from my camera's Secure Digital memory cards to my Mac, I now use an ExpressCard reader. Devices such as the SIIG Express-Card 11-in-1 Reader/Writer can read and write to plenty of card formats, such as SD or Sony Memory Stick.
They're a bit faster than the Mac's USB 2.0 port; in my testing, 1.2GB of digital photos transferred about 26 seconds faster via the ExpressCard (1 minute and 23 seconds) than over a USB cable connected directly to the camera (a Nikon D80) equipped with USB 2.0 (1 minute and 49 seconds).
Be sure to get the right card for your MacBook Pro: An ExpressCard/34 (such as the EZQuest 2 Port eSATA PC ExpressCard, left) will fit, an ExpressCard/54 (right) won't. ExpressCards generally also sit flush with the MacBook Pro's case, so you can leave them in the slot all the time, rather than popping them in and out. (The exception: ExpressCards that read CompactFlash memory.) Be sure to pay attention to the cards' specs as you shop. Many models can't read SDHC (Secure Digital High Capacity) cards with capacities greater than 4GB.
ExpressCards can also provide something that isn't otherwise available on a Mac laptop: a way to connect external hard drives that support the faster eSATA (external Serial ATA) interface. With a maximum throughput of 2.5 Gbps, an ExpressCard comes close to keeping up with eSATA's 3-Gbps capacity. (These numbers are theoretical maximums; real-world performance rarely matches them due to system overhead and other factors.) Some eSATA ExpressCards offer more than one connector, so you can connect multiple drives.
Don't want to tether your laptop to an external drive while you're traveling? You can also get ExpressCards that have solid-state storage of their own, such as the Delkin ExpressCard 34 Solid State Drive 16GB.
A MacBook Pro includes a limited number of USB and FireWire ports. You can add more cable connections via the ExpressCard slot. Its high capacity provides plenty of bandwidth to handle multiple FireWire 800, FireWire 400, and USB 2.0 ports, or combinations of those.
Using an ExpressCard to multiply your ports means that you can leave other hardware at home: these cards can replace a dedicated USB hub, so that's one less thing to pack in your laptop bag. You can also forget your hub's AC power brick. Because an ExpressCard with multiple USB ports lets you charge your phone (with the appropriate cable), iPod, and other items, you can leave their respective power bricks at home, too. And you won't pay a performance penalty: in my testing, I found no significant speed difference between copying large files via ExpressCard versus the MacBook Pro's built-in ports.
ViDock Gfx One of the more interesting uses of the ExpressCard slot is to connect multiple monitors. You can already connect one external display to the laptop's DVI port. But Village Tronic's ViDock Gfx lets you connect up to three displays--four, if you count the MacBook Pro's own screen. The ViDock is a separate box with two DVI-I ports for connecting the displays and adapters; it can also output SIIG Express-Card 11-in-1 Reader/Writer2 with an adapter (not included). The ViDock has 256MB of video memory that can drive screens at up to 2,560-by-1,600-pixel resolution, and there are no drivers or software to install.
(The ViDock Gfx initially was incompatible with first- and third-generation MacBook Pros; Village Tronic is working on the issue with Apple.) Also, be warned: Its fan is pretty darned loud.
And Much More
This list barely begins to cover the range of ExpressCards available for the MacBook Pro.
Then there are miscellaneous cards such as the SiK Rex, a remote control that stores handily in the ExpressCard slot (it doesn't actually connect to the ExpressCard circuitry); SIIG Express-Card 11-in-1 Reader/Writer88 VoIP phones; and even serial and parallel port adapters. The Delkin ExpressCard 34 Solid State Drive 16GB2 offers a lengthy list.
If you own a MacBook Pro, you probably chose it because it offers more than the MacBook--a larger screen, better video memory, and FireWire 800. Its ExpressCard/34 slot lets you add even more capabilities.
[Jeff Carlson is the managing editor of Delkin ExpressCard 34 Solid State Drive 16GB3 and the author of The Apple TV Pocket Guide, second edition (Peachpit Press, 2008).]