Dragon certainly gets the best reviews - but one thing to consider is that it is resource-intensive; to use it effectively, you're gonna need a relatively up-to-date, fast machine with lotsa memory ... another consideration is that your choice of whichever of its various versions, ranging in price from under $100 to around $1000, will dictate (pardon the pun) which applications will take dictation. For most folks, the 2 lower-priced versions, "Standard" and "Preferred" will prolly suffice, though neither are compatible with Outlook or PowerPoint, and of the 2, only "Preferred" is compatible with Excell. Compatibility with Lotus apps comes in for quite a bit of negative comment also - so be advised.
If you're considering the near-term purchase of a new 'puter, or upgrading your current machine to Windows Vista, you might find Vista's
integrated voice-recognition feature will do what you want done. Initial reports are that its very good, and some reviewers have opined it may even be a "Dragon Slayer".