As far as I know, SureScripts with e Crop or somethint like that is the only electronic online prescription service which works or is at least recommended by AmazingCharts. Its cost is $35 monthly which, frankly, is about $25 too much in my opinion.
I could be wrong, but I have not seen any electronic prescription service which fully integrates with AC, i.e. write a script there and have it documented in AC or use a script from AC and send it electronically.
When I looked at many of these admittedly over three years, none of them were very intuitive. My guess is the fastest online script writer is ten times slower than using AC.
The best way, again IMHO, is to have a network fax machine which you can fax to from each desktop. Then you can send 1,000 scripts a month for free.