Shown below is a monthly survey of traffic data for the top 25 largest web 2.0 sites ranked by a combination of Compete and Quantcast data. For each site, unique U.S. monthly visitor data as well as respective rank is showed. For entries where a wide range exists between the two data sets the highest numbers were used for ranking purposes. Although no traffic metrics are completely accurate you can believe the data below to be useful for gauging relative audience size.

1 | MySpace.com
67,654,880 Unique Monthly Visitors (United States) – Rank: 6 – Compete
49,000,000 Unique Monthly Visitors (United States) – Rank: 6 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

2 | Wikipedia.org
46,716,672 Unique Monthly Visitors (United States) – Rank: 10 – Compete
49,000,000 Unique Monthly Visitors (United States) – Rank: 7 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

3 | YouTube.com
43,798,702 Unique Monthly Visitors (United States) – Rank: 12 – Compete
30,000,000 Unique Monthly Visitors (United States) – Rank: 15 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

4 | FaceBook.com
20,284,357 Unique Monthly Visitors (United States) – Rank: 29 – Compete
20,000,000 Unique Monthly Visitors (United States) – Rank: 26 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

5 | PhotoBucket.com
24,197,063 Unique Monthly Visitors (United States) – Rank: 22 – Compete
14,000,000 Unique Monthly Visitors (United States) – Rank: 30 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

6 | CraigsList.org
21,291,669 Unique Monthly Visitors (United States) – Rank: 28 – Compete
13,000,000 Unique Monthly Visitors (United States) – Rank: 41 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

7 | flickr.com
17,613,649 Unique Monthly Visitors (United States) – Rank: 40 – Compete
8,000,000 Unique Monthly Visitors (United States) – Rank: 81 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

8 | digg.com
22,637,952 Unique Monthly Visitors (United States) – Rank: 24 – Compete
6,900,000 Unique Monthly Visitors (United States) – Rank: 99 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

9 | Topix.com
19,597,055 Unique Monthly Visitors (United States) – Rank: 34 – Compete
2,100,000 Unique Monthly Visitors (United States) – Rank: 545 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

10 | WordPress.com
3,931,787 Unique Monthly Visitors (United States) – Rank: 369 – Compete
12,299,776 Unique Monthly Visitors (United States) – Rank: 44 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

11 | Netscape.com
4,921,378 Unique Monthly Visitors (United States) – Rank: 274 – Compete
8,359,018 Unique Monthly Visitors (United States) – Rank: 76 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

12 | TypePad.com
6,279,908 Unique Monthly Visitors (United States) – Rank: 189 – Compete
5,000,000 Unique Monthly Visitors (United States) – Rank: 154 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

13 | CafePress.com
3,335,308 Unique Monthly Visitors (United States) – Rank: 452 – Compete
3,200,000 Unique Monthly Visitors (United States) – Rank: 305 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

14 | Feedburner.com
6,339,449 Unique Monthly Visitors (United States) – Rank: 187 – Compete
536,100 Unique Monthly Visitors (United States) – Rank: 3,151 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

15 | Xanga.com
3,717,917 Unique Monthly Visitors (United States) – Rank: 398 – Compete
1,800,000 Unique Monthly Visitors (United States) – Rank: 669 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

16 | Technorati.com
3,329,262 Unique Monthly Visitors (United States) – Rank: 453 – Compete
1,600,000 Unique Monthly Visitors (United States) – Rank: 781 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

17 | LiveJournal.com
3,235,686 Unique Monthly Visitors (United States) – Rank: 470 – Compete
1,900,000 Unique Monthly Visitors (United States) – Rank: 657 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

18 | Last.fm
1,341,209 Unique Monthly Visitors (United States) – Rank: 1,339 – Compete
1,100,000 Unique Monthly Visitors (United States) – Rank: 1,335 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

19 | DailyMotion.com
1,681,495 Unique Monthly Visitors (United States) – Rank: 1,030 – Compete
788,864 Unique Monthly Visitors (United States) – Rank: 2,006 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

20 | Friendster.com
1,375,045 Unique Monthly Visitors (United States) – Rank: 1,303 – Compete
818,081 Unique Monthly Visitors (United States) – Rank: 1,926 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

21 | LinkedIn.com
1,244,871 Unique Monthly Visitors (United States) – Rank: 1,464 – Compete
1,000,000 Unique Monthly Visitors (United States) – Rank: 1,425 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

22 | iStockPhoto.com
1,018,658 Unique Monthly Visitors (United States) – Rank: 1,850 – Compete
999,938 Unique Monthly Visitors (United States) – Rank: 1,499 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

23 | del.icio.us
973,908 Unique Monthly Visitors (United States) – Rank: 1,930 – Compete
1,100,000 Unique Monthly Visitors (United States) – Rank: 1,341 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

24 | StumbleUpon.com
660,450 Unique Monthly Visitors (United States) – Rank: 2,932 – Compete
688,950 Unique Monthly Visitors (United States) – Rank: 2,339 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007

25 | MyBlogLog.com
2,461,599 Unique Monthly Visitors (United States) – Rank: 650 – Compete
50,946 Unique Monthly Visitors (United States) – Rank: 4,794 – Quantcast
eBusiness News | Top 25 Largest Web 2.0 Sites | Posted 6/09/2007