This is a list of packages that are installed on my router but do not appear to be in the pptp image.
I used the pppoe image.
packages with "?" do not appear on my system but seem to be installed in the pptp image according to:
http://wiki.openwrt.org/OpenWrtDocs/Installing#head-1a60a7c16a58cbcb8ba1434325f4f24567b0b965

curl
ip
kernel
kmod-gre?
kmod-pppoe
kmod-tun
libcurl
libelf
liblzo
libncurses
libnetsnmp
libopenssl
nas
ntpclient
pptp?
ppp-mod-pppoe
snmp-utils
snmpd
zlib