I don't have a desktop computer at work. I'm one of the many who have given up on the big boxes and simply use a laptop for everything. The problem is that laptops are often short on the high-end hardware that makes desktops so enjoyable. Here are a few add-on's that you can use to help you get the most from your laptop.
More screen real estate
My biggest complaint with laptops is the lack of screen real estate that I enjoy on my home system. Most laptops have a VGA out, but what if you want a second large external monitor? The solution is the Tritton SEE2 USB to VGA adaptor.
At about $80, this adaptor plugs into a USB 2.0 port and lets you drive an external monitor, up to 1600x1200, a respectable resolution for any portable machine. It draws enough power from the USB port that it doesn't require any other power source so you can throw it in your bag and go. The Tritton SEE2 also supports 1680x1050 widescreen, which has been a common resolution for wide format LCDs lately. [Update: Yes, the Tritton SEE2 supports Vista.]
More graphics horesepower
Let's say you're generally happy with the CPU power of your laptop, but the graphics card is too lame to support your gaming habits. You're stuck, right? Not necessarily. If you have a ExpressCard|34 slot and can afford it, you could use the Magma ExpressBox1, an external PCI-E expansion. This pricey little box (at $700+) will let you use a full-sized PCI-E graphics card on your laptop.
One downside is that the ExpressBox1 only supports video cards that use up to 55 watts of power, but that will get you up to a Radeon X800 XL (see this chart for more details on video card power consumption.)
It's hard to believe you can run a high end video card off a card slot, but the "theoretical" max throughput with ExpressCard is 2000Mbps so game on. Magma is working on a new version that will house "double-wide" video cards.
The wall of sound
If your laptop has an integrated speaker system that is one step beyond a string and two cans, amp it up using the Creative Labs Sound Blaster X-Fi (Xtreme Fidelity).
Coming in at an affordable $108, the X-Fi is an ExpressCard|54 solution that will delivery 24-bit/96kHz Dolby 7.1 surround sound with an improved Audigy 4 board.
The X-Fi supports optical in/out, includes a speaker dock (an external dongle to plug in the speakers) and has MP3 fidelity enhancement built-in.
Where to put it all
I don't know about you, but I've never had a laptop with as much drive space as I would like. The best solution I've found is the 250GB Western Digital Passport ($160, Channel 8 logo sold separately.) The Passport is about the same size as a Zune and holds a massive 250 gig of data. Because it uses a 2.5" drive, it easily fits into a pocket and doesn't require an external power source. This one goes everywhere with me. Just make sure you back it up to your Windows Home Server and use BitLocker in case you lose it. I ditched the cable that came with the drive and picked up a very nice retractable USB cable.