TECHNOLOGY: Market Place; Dragon Systems, a Former Little Guy, Gets Ready for Market
Market Place column on speech-recognition software produced by Dragon Systems, company scheduled to sell shares to public in next few weeks; Dragon Naturally Speaking software converts words spoken conversationally into computer's microphone into words typed on computer's screen; Dragon Systems has balance-sheet strength and good products and young and extremely fluid market niche; potential problem is with large companies like IBM, Royal Philips Electronics and Microsoft, all of which are working on similar speech technology that they might try to bundle into their hardware; photos; graphs (M)