Howto: Get Command Line on your G1, kill processes and more!

First grab pTerminal via the app market, then run "ps" without the quotes, then you can issue the standard kill command like so:
kill 797

Note: 797 is a test process identifier, so you'll need to see the pid with the ps command.

So far I have been able to use these commands:
# cd /system/bin
# ls
rmdir
dmesg
renice
dumpcrash
rm
reboot
printenv
dd
ps
date
notify
cmp
netstat
chmod
mv
cat
mount
wipe
mkdosfs
watchprops
mkdir
wpa_supplicant
wpa_cli
wlan_loader
toolbox
telnetd
vmstat
system_server
svc
surfaceflinger
ssltest
lsmod
sh
servicemanager
service
sdutil
sdptool
rild
umount
radiooptions
qemud
pm
playmp3
ls
ping
netcfg
mountd
monkey
mediaserver
logwrapper
top
logcat
linker
itr
installd
log
input
htclogkernel
hostapd_cli
hostapd
hcid
hciattach
sync
flash_image
fillup
dvz
dumpsys
ln
dumpstate
dhcpcd
dexopt
debuggerd
debug_tool
dbus-daemon
stop
dalvikvm
app_process
am
akmd
kill
start
ioctl
smd
insmod
sleep
iftop
setprop
ifconfig
setconsole
id
sendevent
hd
schedtop
getprop
route
getevent
rmmod
df