Installing 2 or more Monitors

Can any help me with this? I have dimension 2400, which is the best most reliable and cost effective options to install 2 or more monitors to run different applications at the same time? I intend to install a maximum of 3 monitors, but for now I have 2 to go with. I learnt a video card is involved, Which type? Dual head video card or  what? Please list best  possible optons.

 

PS.Just thinkin if  the following info might be helpful; I will be upgrading my memory to 2G from 512MB. I have 3 PCI slots, one empty, one with a TV card which am no longer using so can be discarded, and the third one has got a card in it which I think is for Dial-up modem use, I use broad band any way.