Scheduling service calls software

What software have you found to be the best or most efficient at schedueling appointments with customers? I'm in the plumbing & hvac business and right now, we've always done it with "paper and pencil", but we're looking for something computerized. Thanks in advance!
Jeremy
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There is a calendar set up in Socal Service Manager. You might want to look at the write up on it at http:\\WWW.SBTBILL.COM
Bill Couture
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