Sub woofer for laptop

Some laptops advertise 'subwoofers' built into them, however in all actuality they are midrange speakers. Seem to add at least and bring it to a somewhat full range sound from a high end tinny sound, however not truly subs since they really only help down to about 200 Hz. If you are looking for something mmore powerful than that I would suggest headphones or a small speaker setup. Most subs require amplification of some sort which means more power so one without a wall outlet somewhere along the line probably wont happen unless you want to dish out major dollars. At least good quality ones.

Seablade

My Gateway M505XL has a built-in subwoofer and I love it. I can't imagine watching DVD movies or listening to music without the subwoofer built into my laptop as I can bring it anyway without external speakers.

I second this. I'm currently researching a high quality headphone setup to be used with my laptop for composing music. I'll post my findings and hope someone finds them useful. They echo the opinions of many people at head-fi forums (www.head-fi.com) which is the place to go if you need more information about headphones.

I like BIG and accurate bass so my headphone of choice is Beyer dynamic 770 / 80 ohm version. It costs around 150$, but from what I hear it sound shit without a good headphone amp to drive it. All the recommended models are over 300$ and I'm struggling to find the cheapest sufficient option. With the right amp though, the 770s become the grooviest headphones around for bass-lovers.
The sound signature of these cans is: deep, powerful and accurate bass which is too much for some people (hence the nickname "darth beyers"). Good soundstage (although certainly not the best), which is good for gaming, classical music, electronic music and music in general, which needs the feel of "space" to sound the best. The sound in general can be described as very dynamic and exciting with a hint of sibilance at times (high sounds can sound too shrill at times). Whether you find them sibilant or not is very individual though.

If you want better soundstage and more balanced sound at the expense of deep bass, look into Audiotechnica a500 / a900 or Sennheiser 580. If you have golden ears, consider also Sennheiser 600 / 650 which have minor improvements over the sound of the 580 but cost a lot more. All of these cans need amplification to sound good. The Sennheisers have a beautiful laid back sound which is good for long relaxing listening but not for rocking hard.

Another and cheaper option for a good bassy headphone would be Ultrasone 650, which is more easily driven and costs around the same as the 770s. It has less soundstage and bass but reproduces high sounds better. For more info read gsferrari's mini-review on the Ultrasone 650s.

If you don't need soundstage and like rock music, the absolute best value headphone would be the Grado sr60, which is easily driven without an amp and looks cool to boot, although many people complain about the comfort and build quality. They cost about 60$ and the sound quality is amazing.
If I didn't need the extra-deep bass and soundstage (the grados have none), these would be my weapon of choice.

If you need something very portable, I recommend the Sennheiser px-100s which I have. They cost about 40$, take little space, are built good and sound very good for a headphone this size/price. I prefer these over the Koss Portapros, which have bigger but a bit bloated bass and don't feel as comfortable on my head.

Don't buy any of these headphones based on only this post. This should serve only as something to get you going. Make your own research so you won't be disappointed.