i still prefer real analogue hardware for synthesis,but use vsts also..
just my opinion,after comparing some vsts against hardware,,
a few pay for vsts that are worth a a look,
analogue synthesiser emulation
gmedia -imposcar
arturia -minimoog
arturia -modular
arturia -jupiter8v
vocoder
eiosis - els vocoder(model of ems5000)
a couple of usefull free bits
vocovee - freeware vocoder
http://www.kvraudio.com/get/3433.html
gtg3 drumsampler.