Say what you will about the small footprints of Asus' Eee PCs, the notebooks are a tad thick for their overall size. Both the Eee PC 901 and the 1000 measure about 1.5" at their thickest points, which is about in line with full-sized consumer laptops.
The good news is that Asus has a thinner Eee PC in store. HKEPC has posted some details and a couple of photos of the Eee PC S101, which looks like a fancier cousin of the 1000. The S101 will have a 10.2" display, a 1.6GHz Intel Atom processor, an Intel 945 GME chipset, and either 32GB or 40GB solid-state drives depending on the exact variant. Those specs look similar to those of the Eee PC 1000, but HKEPC claims the S101 will be just "16 ~ 21mm" thick (about 0.63"-0.83").
What's the bad news? HKEPC goes on to say 32GB and 40GB variants of the Eee PC S101 will cost a respective $699 and $899 when they come out in mid-September. These prices match those in reports of luxury Eee PCs we saw recently, and the S101's glossy black-and-brown enclosure certainly seems to fit the part. For 900 bucks, though, we suspect most folks would rather get a more feature-rich laptop like Dell's XPS M1330.
Update: HKEPC's article seems to alternately mention 40GB and 64GB SSDs for the pricier of the two S101 systems.