ACH Direct is a company with which I have had personal experience,
and I found them to be very good.
The following is from their "Corporate Overview" web page.
"ACH Direct is one of the fastest-growing privately held electronic
funds transfer processors in the United States, with over $5 billion
in transactions processed in 2005."
The comment by nelson-ga is a valid one, in that your bank might
have an ACH solution, or you might be able to use third-party ACH
software with your current bank.
"EZ-ACH" is one such third-party ACH software company.
"EZ-ACH allows you to simply and efficiently enter your financial
information and with just a few clicks of the mouse, create a NACHA
formatted ACH Origination File ready to be processed by the Federal
The "EZ-ACH Frequently Asked Questions" (FAQ) web page suggests that
you speak with your bank as well.
"There are many reasons why we encourage you to talk to your bank or
credit union before making the decision to purchase our software.
For one, some banks prefer to use their own proprietary software for
ACH processing. Another reason is that not all banks process ACH
files. Some banks prefer raw data be sent to them for processing.
Others will happily accept your ACH Origination file created by
EZ-ACH. We want you to be confident in your purchase of EZ-ACH."
This "dmoz" listing shows there is no shortage of ACH processors.
"... Merchant Services: Check Processing [44 listings]"
As your specific needs, such as repetitive payments, or online
shopping cart processing, etc. might be better addressed by one
company versus another, I suggest you start with the dmoz list to
see if there is a good match for you.
If you need any clarification, please feel free to ask.
Search strategy: Personal experience.
dmoz search on: ACH
Looking Forward, denco-ga - Google Answers Researcher