Microblogs are world's first instant global mass media.

Microblogs are here to stay and the most important thing about microblogs is their immediate feedback information loop capabilities.

Some microblogs worldwide

This list is a personal choice and based on three criteria: ease of operability, quality of service and experienced functional up-time.

general
http://twitter.com
http://jaiku.com
http://pownce.com
http://yelago.com
http://beemood.com
http://yonkly.com


Chinese
http://fanfou.com
http://zuosa.com
http://komoo.cn

Indian
http://snockles.com

Singaporean
http://tiish.com

Italian
http://meemi.com

Spanish
http://khaces.com
http://fritsi.com

Turkish
http://nolyo.com

French
http://noumba.net
http://tapioka.ca
http://frazr.com

Korean
http://playtalk.net
http://me2day.net

Japanese
http://feecle.jp
http://haru.fm

German
http://niimo.com
http://dukudu.de

Polish
http://blip.pl

Dutch
http://numpa.nl

Portuguese
http://gozub.com

Russian
http://smspr.ru

Arabic
http://watwet.com

Romanian
http://cirip.ro

Mexican
http://mexicodiario.com

special
http://tumblr.com
http://hictu.com
http://babl.nl
http://floort.com
http://help.com
http://justtell.us

multiple posting

http://hellotxt.com


The most exhaustive list I know about is the list made up by thw http://www.thws.cn/articles/twitter-clones.html

Pieter Jansegers

http://microblogs.ning.com

I wrote 

also  Microblogs are changing the world

and  Why twitter is such a great success…