Inexpensive light-weight mini computers called netbooks have been getting a lot of press lately. If you have noticed, the larger merchandisers, like Costco and Walmart have started prominently featuring these computers in their store displays.
Prices for these smaller laptop computers start at about $250. Much larger than a PDA or iPhone, but smaller than a full-size laptop, they often come with a 9" monitor and smaller hard drive options. Although in this context smaller is definitely relative, today's smaller drive is very large by yesterday's standard. Most of the models come with an operating system, in some cases Linux and in others Windows XP Home. They usually weigh about 2 to 2 1/12 pounds. They are called "netbooks" because they are supposedly used to connect to the Internet.
The most common criticism is the size of the keyboard, but most models come with at least one USB port and it may be possible to plug in a larger and more comfortable keyboard. But, that would essentially defeat the idea of the smaller, cheaper computer. If you want a full-size keyboard and mouse, you can purchase desktop computers starting at $499 with a 17 inch flat panel monitor. A Dell Inspiron computer, by itself without keyboard or monitor, starts at $279.
Check Wikipedia for a huge comparison chart of the different models of netbooks. The apparent low price of the netbooks has a trade off in fewer options and less utility. If you need a primary computer to work on for long periods of time, you may wish to spend a little more money and get a full sized, desktop computer.
The main issue with netbooks is portability and convenience. One of the main reasons for the netbook's development was to extend the market for computers to less developed countries. It is inevitable that the netbooks will become more expensive with additional storage space and options, but there seems to be a market for these very small sized computers.
If you are thinking about a second computer for on-site research, you may wish to take a look at these smaller and much lighter options.