For simple projects and residential we prefer specs on drawings as do our clients and contractors. For larger or complex projects where book specs are in order we use BSD SpecLink. Their annual subscription is approx. $3k. For us as occasional spec writers we find the interface and reference info helpful and simple to use. If money is an issue, I've seen some free master specification resources on line but don't recall names or web sites. I also found (but didn't note or bookmark) an interesting software package that generated specs to be placed in CAD sheet files and tightly coordinate with CAD drawings for call-out notes. As I recall the cost was somewhat less than SpecLink.
Eric Gresla, AIA