For those looking to read manga on their PC,
here are a couple of good sites:

http://hanashi.org
http://www.rawmanga.com

Does anyone know any others?
I prefer sites specific for Japanese manga (and not general sites/trackers).

Thank you.

In Japanese or in English?

As the 2 sites listed are only for raws, I'm going to assume 'in Japanese' is the answer.

Unfortunately, I haven't got any sites to add to this list.

manga helpers
baka updates

This site has both translated and raw manga:
http://gotlurk.net/?action=home
Its downloads are via IRC though, but I think that won't be a problem for anyone here. By the way, the name of the raw manga bot is [UR]DAN.

http://raw-manga.blogspot.com/
http://jcafe.vnmanga.com/index.php?board=44.0
http://ddl.aznman.net/