well, I'm not posting something extra ordinary, but here is the list of top web 2.0 sites, all can give you multiple backlinks.
wikispaces.com 7
squidoo.com 7
hubpages.com 7
wordpress.com 7
tripod.com 7
webs.com 8
livejournal.com 8
blog.com 6
blogspot.com/ 6
jimdo.com 7
gather.com 6
zoho.com 6
blog.friendster.com 6
bravejournal.com 6
sosblog.com 5
onsugar.com/ 5
blurty.com 5
insanejournal.com 5
soulcast.com 4
inube.com 4
experienceproject.com 5
typepad.com 5
wikidot.com 7
thoughts.com 7
multiply.com 7
weebly.com 8
shutterfly.com 8
pulse.yahoo.com 8
advogato.org 6
wikia.com 7
wix.com 6