The word means 'students' or 'learners'.
How you spell it depends on which language you translate it from. The BBC have always prefered the spelling from Persian which is Taleban. The Americans prefer to translate from Arabic and it comes out as Taliban and most other British media follow the American way of doing things.
The Times uses Taleban, and the Telkegraph uses Taliban. Both are correct.
The BBC have always prefered the spelling from Persian which is Taleban, see this example from BBC website in 1997
http://news.bbc.co.uk/1/hi/world/west_asia/370 21.stm