Hello Erica,
I've used several TTF barcode fonts and they print out easy on inkjet and laserprinters. Not much luck on most matrix printers. Don't forget the opening and closing '*'
There's a barcode 39 font right here at UT in de download section. As for reading them, most readers are able to read barcode 39 by default but on some scanners different symbologies must explicitly be enabled.
You might also consider printing barcodes on special barcode printers such as TEC and Zebra. They handle all the start an stop symbol stuff so you don't have to worry about that. A good barcode printer driver allows you to select a printer font and set most properties in the driver settings. In most cases, you won't be able te preview barcodes on the screen however because windows cant read all font info from the driver.
If you've got more questions just ask, we've been doing bc39 for ages.
jeroen@softwear.nl