If you have a midi keyboard and are interested in a fantastic sound package, then check out Korg´s Legacy Digital Edition. Its a faithfully recreated emulation of both the classic M1 synthesizer and the Wavestation workstation. It works as a standalone software or as a VST/AU/RTAS plugin (basically that means that they integrate into your DAW software if you are using Cubase/Garageband/Logic). I made my latest backing track using this.

http://www.korg.com/product.aspx?pd=443