Google describes PageRank (PR) as
“PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page’s value. In essence, Google interprets a link from page A to page B as a vote, by page A, for page B. But, Google looks at more than the sheer volume of votes, or links a page receives; it also analyzes the page that casts the vote. Votes cast by pages that are themselves “important” weigh more heavily and help to make other pages ‘important’.”
Webmasters just dream about getting PageRank 10. Though it is unofficially proved that PageRank has very little effect on SERP, webmasters would do anything to achieve higher PR. There are webmasters or SEO companies who don’t even slightly hesitate to apply Black Hat SEO / spamming for PR even though know they might be blacklisted in Google.

Anyway, here is a list of PageRank 10 websites according to Google PageRank update on April, 2008.

Title	PR	Google Banklinks	Yahoo! Backlinks	URL:
Adobe	10	82,600	2,869,228	http://www.adobe.com/
World Wide Web Consortium	10	166,000	2,778,033	http://www.w3.org/
Macromedia	10	31,600	738,824	http://www.macromedia.com
U.S Department of Energy	10	43,000	1,832,883	http://www.energy.gov
National Aeronautics and Space Administration	10	64,400	1,638,342	http://www.nasa.gov
Google Search	10	3,830,000	264,426,369	http://www.google.com
National Science Foundation	10	27,100	1,512,528	http://www.nsf.gov
The White House	10	67,800	1,765,906	http://www.whitehouse.gov
Real Media	10	130,000	1,789,753	http://www.real.com
US Goverment website	10	142,000	32,776	http://www.usa.gov/index.shtml

For last couple of year, I’m taking active part in different SEO forums. One of the most common asked question is “How can I get quality backlinks?” or “Why I can’t find my backlinks?” etc etc. Anyway, I’ve come across a list of “dofollow” social bookmarking website lists. Hope none need any introduction with “dofollow” and “nofollow” link attribute.
According to Wikipedia, nofollow is an HTML attribute value used to instruct some search engines that a hyperlink should not influence the link target’s ranking in the search engine’s index. It is intended to reduce the effectiveness of certain types of search engine spam, thereby improving the quality of search engine results and preventing spamdexing from occurring in the first place.

rel=”nofollow” Action	Google	Yahoo!	MSN Search	Ask.com
Follows the link	Yes	Yes	Not proven	Yes
Indexes the “linked to” page	No	Yes	No	Yes
Shows the existence of the link Only for a previously indexed page	Yes	No	Yes
In SERPs for anchor text	Only for a previously indexed page	Yes	No	Yes

Here is the list of “dofollow” social bookmarking websites (updated on 31st May, 2008):

Title	Current Google PR	Google Backlink	Yahoo! Backlinks	URL
Backflip	6	502	33,059	http://www.backflip.com/
Bibsonomy	7	2,300	779,947	http://www.bibsonomy.org/
LinkaGoGo	6	129	59,769	http://www.linkagogo.com/
Mister-Wong	7	67,500	8,979,013	http://www.mister-wong.com/
Spurl	6	1,990	4,945	http://www.spurl.net/
Buddy Marks	5	80	807	http://www.buddymarks.com/
MyLinkVault	5	53	11,587	http://mylinkvault.com/
SpotBack	5	2,590	762	http://spotback.com/
A1 Webmarks	4	43	13,108	http://www.a1-webmarks.com/
ClipClip	6	3,270	16,269	http://clipclip.org/
Connectedy	5	72	11,207	http://www.connectedy.com
OYAX	4	253	58,771	http://www.oyax.com/
MyVmarks	5	459	104,445	http://www.myvmarks.com/
TeDigo	4	7	191	http://www.tedigo.net/
Complore	4	74	17,295	http://www.complore.com/
Ez4U	3	41	759	http://ez4u.net/
Info4it	3	25	139,289	http://www.info4it.com/
MyPIP	3	13	407	http://www.mypip.com/
Space-Ed	3	1	9	http://space-ed.com/
SyncOne	3	27	6,792	http://www.syncone.net/
Yattie	3	5	529	http://www.yattle.com/
Upchuckr	4	44	625,647	http://www.upchuckr.com/

Source of the list – Caroline Middlebrook