We are an IT company who operates a B2B portal. what is the best and
cheapest software package available in the market that can help in managing 
our whole office of an e company (open source is more prefarable)
which can  remove paper work, payrol,
employ management,
time attendance, task management, employe performance, work flow,
document, forum, instant messaging, employe availability,
accounting,  and what ever is required for a company running a
ebusiness like portals.

i think my suggestion is MS-Office is very user friendly and very best
software in the office management system..

and i suggest u go on Open office which is free of cost..
it is also flexible one..