China Travel Tours Transportation company, a subsidiary of China Travel Service (CTS), runs a full range of bus services between Hong Kong and neighboring mainland cities, such as Guangzhou, Dongguan, Foshan, Shunde, Panyu, Zhongshan and Zhuhai.
Its website lists schedules as well as prices. So it is a wonderful reference. But to see the full list of its bus services, you must click on the names of place/border crossing/route on the left navigation bar. You will be surprised how many more bus destinations you can find.
The website is