Is there a cable available that will connect an I pad to an older printer?

No, the iPad connects only by wireless for printing.

If your printer is AirPrint compatible, you should be able to print without any further modifications. Check this Apple support document to see if your printer is AirPrint compatible:

http://support.apple.com/kb/ht4356

If your printer is not AirPrint compatible, you might want to try an App like Print Central on the iPad to see if it might recognize the printer and allow you to print over the wireless network. Most printers will work, but unfortunately there is no way to know whether your printer will work until you try.

PrintCentral for iPad on the iTunes App Store

If you have a Mac or PC there are utilities available that enable them to act as a print server, enabling you to print to any printer the Mac or PC can use.

The donation-supported handyPrint and a commercial product such as Printopia ($19.95 with free trial) are two examples. The Mac must be "on" but may be asleep for them to work. Equivalent PC options may exist but you're on your own finding them.

You can also buy this standalone print server:

http://www.lantronix.com/it-management/xprintserver/xprintserver.html

These options enable you to use any printer available to your network, even older ones that may predate AirPrint by decades. But as Bob said, everything you do with an iPad is wireless.

>Equivalent PC options may exist but you're on your own finding them.

Collobos has the PC version version.