Due to the popularity of the Joomla! open source cms a number of professional and free joomla templates are available across the internet which you can download and install directly onto your joomla web site.

Free Joomla Templates
1) mambohut - contains hundreds of  free Joomla templates
2) joomlaya - contains close to 600 free templates
3) joomlaos - lots of free templates to download.

Professional joomla templates

1) Joomladesigns - joomladesigns offer over 100 professional joomla templates