A lot of OKI laser printers and MFPs support PostScript. Those will work fine with the generic PostScript PPD (Driver). If this is a network printer, remember that 10.6 no longer supports AppleTalk, so you will have setup the printer via it's IP address (Print a test/configuration page, or look at the front control panel on the printer). Please double check the subnet/mask to make sure the printer is reachable by your computer. You may have never setup the IP address of your printer. So you might have to find that manual. When have the good IP address of the printer, you can manually setup the Printer in Add Printer (in Print & Fax Prefs). You will have to pick a Protocol. Try JetDirect first. Second LPD. Note if this is a USB printer, just plug it in...no IP address needed! The Driver you will to select will be the Generic Postscript PPD (driver). For the adventuresome, you could also copy the PPD file for the OKI printer from your 10.5 system (/Libraries/Printers/PPDs....) and put it into the sample place on your 10.6 system. (This May work, so I leave this to the reader to sort out those details)
If you have a printer that requires a GDI driver (Many posted here do), your only option for now is setup a 10.5 system that has the driver installed and that can already print to that printer. Once you can print from 10.,5, just enable printer sharing. 10.6 system can print to 10.5 shared printers. You may again need to select the Generic PPD on the 10.6 system. As long as the 10.5 system can print, it will convert the 10.6 PS to a form that the 10.5 driver can use and print. Not Ideal, but at least an answer until OKI updates their GDI driver.
I hope this helps!