Cheapest netbook is the Acer Aspire One A110L @ R1999 (at Incredible, no less)
Specs:
Intel Atom N270 @ 1.6GHz (single core with hyperthreading)
512MB DDR2 RAM
8GB Solid-state drive
8.9" LED-backlit LCD @ 1024 x 600
Wifi (Atheros

)
Card-readers
3 x USB
Webcam
3-cell battery
Acer's Linpus Linux Lite
I also have one of these; it has served me very well; still use it regularly. It weighs 0.99kg, so it's super light. Regardless of what people tell you, 512MB RAM is enough for netbook-usage; browsing, music, etc.
The downside to this netbook is the entry-level SSD; it's quite slow. However, it's still SSD, so you have only one moving part in your machine: the CPU fan. This makes for a very robust little machine!
The Acer Linpus Linux Lite is decent. But if you like a little more (applications and support-wise) you could do what I did: install Ubuntu and never look back
I use the EXT2 filesystem with a few custom mount options, and it does the job really well. However, even the default install runs well (I can run full desktop effects and don't really find it to be slow at all, especially since the Intel graphics drivers were fixed).
XP also runs very well if you install Flashfire.
All-in-all, well worth the R1999!