Graphics, Ports, and Connectivity
GPU: In most cases, a discrete graphics chip isn't necessary; the graphics integrated into the latest CPUs offered by Intel and AMD are more than adequate for business tasks. The exceptions are some of the weaker Atom processors found in netbooks, which aren't up to rendering 1080p video smoothly.
Video Output: If you're looking to perform presentations with your notebook, both the graphics and external monitor ports must match up with any projectors or displays you'll be using.
VGA and HDMI outputs are the norm--VGA for backwards compatibility, and HDMI for the best picture with modern displays. DisplayPort is also fine, as long as you see the DP++ logo, which means you can output HDMI, DVI, and normal VGA using adapters.
WiDi, Intel's Wireless display interface can also be handy for presentations as it obviates the need for running cables, something that can be awkward in many circumstances. It also frees you from having to wait in the queue for a particular meeting room.
An external WiDi adapter for the TV is required, and there is a small lag between what you'll see on your laptop and what you see on the display, but the convenience can be addicting.
Data Ports: An eSATA or USB 3.0 port will drastically speed up backups to an external hard drive, or loading or offloading large amounts of data. If you deal with large files or data sets, look for such ports. Otherwise, USB 2.0 is fine, if not optimal, especially with the plethora of online backup solutions available.
Wi-Fi: These days, no laptop ships without at least 801.11b/g/n Wi-Fi. However, you should check your office environment to see if it uses 5GHz 802.11a, which has long been a mainstay of business Wi-Fi networks. The 5GHz band is now also being used on many consumer routers to separate traffic onto two discrete networks. 802.11a is a plus for business laptops, though not always necessary.
Ethernet: 10/100 ethernet is still found on laptops, and in most cases is perfectly viable, but it is rapidly disappearing. Gigabit is faster, and can help streaming HD video on busy networks as well as making network backups faster--look for it.
Bluetooth: Bluetooth is handy for wirelessly connecting your phone to your laptop to sync addresses. It also lets you leverage a favorite Bluetooth headset for Skype and the like. In some (increasingly rare) cases, it even allows you to tether your phone to your laptop and use the phone's data connection.
Broadband: If you're regularly out of reach of Wi-Fi, a broadband connection like the one on your phone is a good thing to have. Some laptops have integrated broadband antennas so you can use an internal adapter. Otherwise, you'll need a USB dongle for the service you use.
PC Card, Express slots: While PC Card and Express slots have largely vanished from mainstream laptops, they are still widely available in business models. If you have legacy card devices such as a smart card reader, or a Firewire card, make sure the laptop you buy has the slot you need.
SDHC/MMC: This slot allows for superportable removable storage as well as making it easy to load photos and video from digital cameras. If you rely heavily on photos or video in your business, a SDHC/MMC slot is a must-have feature. A MemoryStick or MS might also be useful if you're a Sony user, as Sony uses proprietary memory formats.
Port Adapters: All of the above ports are certainly more convenient when integrated; however, Wi-Fi, Ethernet, Bluetooth, and SDHC/MMC (as well as other cards) can also be implemented easily via appropriate USB adapters.
Travel mice and headphones, as well as flash and optical drives, are items you should consider carrying around with you on your travels. Most laptop vendors will be happy to sell them, but they're readily available online at vendors such as Newegg, Amazon, and elsewhere in more variety.
Travel Mouse: If you spend a considerable amount of time using your laptop, a mouse goes a long way towards achieving that desktop feel and speeding up your workflow.
Headphones: Headphones or ear buds are essential to being able to hear what's happening on your laptop when you're on a plane or other noisy vehicle.
Flash Drives: Flash drives are the preferred medium for backing up or storing data securely. You can find a host of thumb drives that meet the FIPS-140 standard for data encryption and security.
Optical Drive: Some laptops still offer internal optical drives, and they're a must for installing some software or watching movies on DVD or Blu-ray discs. That said, the technology is fading, and with streaming media services and broadband connections proliferating, you can probably meet your entertainment and software installation needs without one.
Unless you regularly burn disks for clients, you're probably better off with an external USB optical drive that you can leave at home when you don't need it.
Parts Availability, Platform Stability
Mainstream consumer laptops are produced, then set adrift whenever the next best thing shows up, even when styling or technology take only a minor step forward. It can be very hard to find a replacement laptop or parts for a consumer machine just a short time after you buy one.
Vendors take special care with business laptops to make sure that parts are readily available for an extended period of time and that models don't change drastically. Typically, basic designs won't alter all that significantly over three to five years, and specific models can remain available in production for as long as two years.
The long shelf life means that you can be sure that replacement units and parts are readily available and that your company won't have to worry about compatibility with upgraded versions. A homogenous laptop fleet is far easier and cheaper to support than an ad-hoc array of machines.
Dell's Latitudes and Lenovo's ThinkPads are good examples of corporate laptop lines. If you desire this kind of stability, you'll pay quite a bit more, but the peace of mind can be worth it.
Most business laptops offer warranties that go far beyond the usual one year offered on consumer units--usually, three years standard with options up to five years. Three years is about the average lifespan for a small business notebook, as SMB users are more apt to retire them in lieu of something more modern.
However, five years is not beyond the service life of corporate units, especially these days, with performance having long ago exceeded "fast enough" for everyday business tasks.
Corporations generally rely on their own IT departments for service, but smaller businesses need vendor-provided 24/7 telephone support, as well as depot and on-site service. These kinds of service are especially important for users who travel frequently, and are not available with a consumer laptop, except as provided by the reseller, few of whom have any international scope.
The key to buying the correct level of service is matching it to your worst-case scenario. If it's possible you could be stuck in a strange city where you don't speak the language or know your way around, on-site service is invaluable. Alternatively, overnight shipping of a replacement or of parts would be adequate if you have decent technical chops. If you never leave town and there's a repair center nearby, then buying such service levels would be massive overkill.