This is for the Slephy CP800 but the procedure is the same (with appropriate individual model info) for other models:
1. copy unzipped drivers (a whole SELPHYCP folder) to:
/Library/Printers/Canon/ (will need your password)
if there is no "Canon" folder, create it
2. stop CUPS daemon (in the Terminal) :
type: “sudo launchctl stop org.cups.cupsd” (will need your password)
3. edit /Library/Printers/InstalledPrinters.plist
under “<key>InstalledPrinters</key>” add:
“<string>MANUFACTURER:Canon;MODEL:CP800</string>”
“<string>MANUFACTURER:Canon Inc.;MODEL:Canon SELPHY CP800</string>”
under “<key>Manufacturers</key>” add:
"<string>Canon</string>"
"<string>Canon Inc.</string>"
4. edit “/private/etc/cups/printers.conf”, add following at the end:
<Printer Canon_CP800>
UUID urn:uuid:fcee70cc-231a-372c-6b90-c0db9cd16eda
Info Canon CP800
Location Your_Computer_Name_!!!!
MakeModel Canon SELPHY CP800
DeviceURI file:///dev/null
State Idle
StateTime 1326417576
Reason offline-report
Type 36868
Accepting Yes
Shared Yes
JobSheets none none
QuotaPeriod 0
PageLimit 0
KLimit 0
OpPolicy default
ErrorPolicy stop-printer
</Printer>
5. copy this Selphy CP800 PPD file to: /private/etc/cups/ppd
6. start CUPS daemon: “sudo launchctl start org.cups.cupsd”
Done! If you haven't made typo, you should see the printer in the Preferences/Print&Scan. Enjoy... ;o)