The reason why there are so few PCIE 1x cards is, there aren't that many native PCIE 1x _chips_ out yet. Sure, one could slap a PCIE-to-PCI bridge chip in front of a normal PCI device, but what's the point as long as we still have native PCI slots?
PCIE videograbber chips exist at least from Philips and ATI, and Tuner cards in PCIE 1x shape are coming. Terratec are already shipping one in Germany, LifeView have announced a couple quite a while ago (not spotted in Germany just yet).
Gigabit network cards are available too.
Potentially, SATA cards could be made as well, PCIE SATA chips are available.
Higher spec I/O chips are mostly PCIE-4x: SATA and SAS RAID chips, dual channel gigabit ethernet, etc blah blah.