Now that people are starting to figure out how to hook various USB gadgets to the 770 I thought I'd start a list of known working peripherals. For the record:

TRENDnet TU-ET100C USB 10/100 Fast Ethernet Adapter
Works wonderfully as long as you have the pegasus.ko kernel module copied into the modules directory /mnt/initfs/lib/modules/2.6.12.3-omap1 It's somewhat of a trick to get the kernel compiled with the right gcc version so you don't have to force a load. Here's a link to it: http://lbattraw.home.insightbb.com/pegasus.ko
You will need to run as root: "insmod /mnt/initfs/lib/modules/2.6.12.3-omap1/pegasus.ko" and then "ifconfig eth0 IP_Address netmask NETMASK broadcast BROADCAST_Address up"
Example: ifconfig 192.168.1.5 netmask 255.255.255.0 broadcast 192.168.1.255 up

2.5" SANMAX External Hard Drive Case
Works perfectly with no problems. You'll need to create a directory to mount it on and then "mount /dev/sda1 /mountdirectory_you_created"

BTC Ultra-Slim Multimedia Keyboard BTC 6100
Works flawlessly, plug and play with no other commands/etc. needed This is a great keyboard for the 770 since it only consumes about 5 mA of power! With plain-jane AAA rechargeable batteries (650 mAH NiMH) you can expect 130 hours of continuous use or 5.4 DAYS. At its thickest point it is roughly as thick as the 770 with its case on. I opened mine up and soldered wires to a 4-AAA battery pack to power it without needing a powered hub to make it work standalone with the 770.