The Vaio SuperSlim line, technically the Vaio 505 line, has been the poster child for ultra-portable computing for the last 5 years. Though it was not the first super slim subnote, nor is it the smallest, thanks to good design and great marketing, it is one baseline standard of so-called "A5" subnote genre.
The 505 line began in 1997 with the first model, the Japanese only PCG-505, from where the line gets it's moniker. It was a Pentium 133 with a 10.4 TFT display that clocked in at 1.35 kilos (about 3 lbs) and 208mm (slightly under one inch) thick when closed. It was an interesting concept because, at the time, many other manufacturers were making machines larger to incorporate larger displays and more features; the 505 removed everything but the bare essentials (no built-n floppy drive, only one PCMCIA slot) so the machine size dictated the display size, not vice-versa. Though it was thought that the western market would never have an interest in such a space-saving design, import requests piled up and sonly decided to start marketing it in the West was well.
Successive generations (505X, 505EX, 505TR.. ad nauseum) have changed options and speeds, but didn't change the basic concept; weights and sizes have remained relatively constant throughout it's life; the screen has been widened slowly and the weight now hits a back breaking 3 3/4 pounds </sarcasm>. Many lessons learned in this arena were put into use later on the Sony Vaio Picturebook, a yet smaller subnote. Another important note is that the 505 line was the first sonly product to include iLink, Sony's version if IEEE 1394.
There are nagging problems, though, as any product will have. Due to the thin-ness of the design, there is little in the way of key travel so typing can feel awkward, and the size doesn't lend much to battery life, though advancements in power management and electron storage have increased the battery life two-fold from the original without increasing size or weight significantly.
The current (as of writting) Vaio 505 is the R505 which ships available with a Pentium !!! 850 and 12.1 inch TFT display.