Here is some important list of web 2.0 sites with PR:
wordpress.com - pr9
tumblr.com - pr8
typepad.com - pr8
weebly.com - pr8
blogger.com - pr8
tripod.com - pr8
posterous.com - pr7
jimdo.com - pr7
yola.com - pr7
squidoo.com - pr7
multiply.com - pr7
angelfire.com - pr7
officelive.com - pr7
rediff.com - pr7
wikidot.com - pr7
webs.com - pr7
webnode.com - pr7
salon.com - pr7
edublogs.org - pr6
webspawner.com - pr6
soup.io - pr6
ucoz.com - pr6
travelblog.org - pr6
gather.com - pr6
springnote.com - pr6
webstarts.com - pr6
moonfruit.com - pr6
journalspace.com - pr6
blog.de - pr6
onsugar.com - pr6
quizilla.teennick.com - pr6
areavoices.com - pr6
freeblog.hu - pr6
blog.com - pr6
blogdrive.com - pr5
blogtext.org - pr5
freeflux.net - pr5
freehostia.com - pr5
zoomshare.com - pr5
flixya.com - pr5
webgarden.com - pr5
ohlog.com - pr5
livelogcity.com - pr5
snappages.com - pr5
sosblogs.com - pr5
visualsociety.com - pr5
insanejournal.com - pr5
alivenotdead.com - pr5
hazblog.com - pr5
hpage.com - pr5
blog.com.es - pr5
350.com - pr5
beep.com - pr5
devhub.com - pr5
blog.hr - pr5
blinkweb.com - pr5
ewebsite.com - pr5
flukiest.com - pr4
bloggum.com - pr4
inube.com - pr4
iseekblog.com - pr4
hipero.com - pr4
blurty.com - pr4
bloghi.com - pr4
wallinside.com - pr4
getjealous.com - pr4
fotopages.com - pr4
wikipages.com - pr4
freeblogspot.org - pr4
myblogsite.com - pr4
spi-blog.com - pr4
2itb.com - pr4
mytripjournal.com - pr4
blogreaction.com - pr4
doomby.com - pr4
blogge.rs - pr4
mywapblog.com - pr4
yousaytoo.com - pr4
publr.com - pr3
blogster.com - pr3
weblogplaza.com - pr3
spyuser.com - pr3
bcz.com - pr3
iblog.at - pr3
honmag.com - pr3
blogpico.com - pr2
evood.com - pr2
uwcblog.com - pr2