Bohemia Express
Runs buses to various European destinations including the UK.
http://www.jizdenky.cz/

Bohemia Express International
Eurolines affiliate with coach services from the Czech Republic to the rest of Europe.
http://www.bei.cz/

British Travel International
American agent for Eurolines, the European coach network.
http://www.britishtravel.com/

Busabout Europe
Hop-on, hop-off bus service which stops off in Prague.
http://www.busabout.co.uk/

Capital Express
Operates a regular coach connection between the Czech Republic and the UK.
http://www.capitalexpress.cz/

Cebus
An express bus service that runs between Prague and Brno several times daily.
http://www.cebus.cz/

Dopravni Agentura P&P
Coach and minibus hire.
http://www.transport.cz/

Eurolines
Intercontinental coach operator with a service to Prague.
http://www.eurolines.com/
http://www.eurolines.cz/ http://www.sodeli.cz/

Jizdnirady.cz
Work out schedules and connections for inter-city coach services throughout the Czech Republic at this site. Just click on the Union Jack to access the English language page. Also, when searching, make sure you put in city names in their original language, e.g. Praha for Prague or Roma for Rome.
http://www.jizdnirady.cz/

Kingscourt Express
London to Prague, via Brno, on a regular basis.
http://designstudio.cz/clients/kce/
http://www.kce.cz/

Student Agency
Runs competitively priced express coach services to destinations in the Czech Republic and in Europe. The website is in Czech only.
http://www.studentagency.cz/

Tourbus Praha
Tourbus Praha sells international bus tickets in Prague. They can also help with rail bookings.
http://www.tourbuspraha.cz/