This is a list the 10 most popular mobile websites (in terms of unique visitors) in different countries according to Opera.

INDIA UNITED STATES RUSSIA
1. google.com
2. orkut.com
3. yahoo.com
4. facebook.com
5. songs.pk
6. wikipedia.org
7. youtube.com
8. zedge.net
9. peperonity.com
10. waptrick.com
1. google.com
2. facebook.com
3. myspace.com
4. wikipedia.org
5. youtube.com
6. my.opera.com
7. yahoo.com
8. espn.go.com
9. accuweather.com
10. nytimes.com
1. vkontakte.ru
2. odnoklassniki.ru
3. mail.ru
4. yandex.ru
5. google.com
6. wikipedia.org
7. spaces.ru
8. seclub.org
9. rambler.ru
10. waplog.net
CHINA UNITED KINGDOM FRANCE
1. kong.net
2. baidu.com
3. google.cn
4. sina.com.cn
5. xiaonei.com
6. qq.com
7. sohu.com
8. hao123.com
9. 163.com
10. taobao.com
1. facebook.com
2. google.com
3. bbc.co.uk
4. live.com
5. yahoo.com
6. wikipedia.org
7. youtube.com
8. bebo.com
9. my.opera.com
10. ebay.co.uk
1. google.com
2. facebook.com
3. live.com
4. lequipe.fr
5. wikipedia.org
6. youtube.com
7. lemonde.fr
8. my.opera.com
9. skyrock.com
10. pagesjaunes.fr
GERMANY ITALY INDONESIA
1. google.com
2. wikipedia.org
3. bild.de
4. youtube.com
5. web.de
6. gmx.de
7. sport1.de
8. facebook.com
9. spiegel.de
10. ebay.de
1. google.com
2. facebook.com
3. gazzetta.it
4. youtube.com
5. corriere.it
6. wikipedia.org
7. repubblica.it
8. yahoo.com
9. my.opera.com
10. ebuddy.com
1. facebook.com
2. friendster.com
3. waptrick.com
4. yahoo.com
5. google.com
6. detik.com
7. peperonity.com
8. digg.com
9. wikipedia.org
10. twitter.com

Opera has just released their monthly report on the state of mobile web (also available as PDF) that highlights key trends in mobile web browsing worldwide and also provides a list of most frequently visited websites in different regions of the world.

mobile-web Google, Facebook, Wikipedia and YouTube are hugely popular among mobile users in every region but Twitter is missing probably because smartphone users prefer using standalone apps and not the main Twitter website to tweet.

These reports are based on usage of Opera mobile browsers (Opera Mini and Opera Mobile) that are quite popular on Nokia and BlackBerry handsets but completely excludes the iPhone user-base. Also, Opera reports do not include any adult websites even if any of them makes it to the top 10 list.