[Hampshire] Sending SMS from a computer?

Hi,

I'm looking for a method to send SMS messages from a computer on certain
scriptable events.

Sending to an email address (which gets converted into an SMS) would
probably be ok, but some other (more secure?) interface would be fine as
well, though I'd prefer to avoid having to automate the filling in of web
forms if I can.

I used to use a free service for this but it has (possibly not
surprisingly) ceased to be.

Another free service would be great, but I'd be willing to pay a small
amount per SMS for a reliable system.

I've seen things about attaching a phone (via serial/USB/IR/Bluetooth) to
a PC and using that to send SMS, but that's not really what I'm looking
for.

Andy