It's been a little while since I've been to Port Columbus airport, but there have been several advertisements on the radio recently for two long-term airport parking lots -- I think they're the "red" lot and the "blue" lot (I suppose it could be red, green, blue -- sorry, I just don't remember). One is a tad bit closer to the airport and runs $6 or $7 a day; the other one runs $5 or $6 a day. If I'm understanding the commercials correctly, these two lots are on International Drive, the road that leads right into the airport terminal area, which means they are practically a stone's throw away from the airport. Both offer shuttles to passenger drop-off.
There is an offsite parking lot -- it used to be called 3-C parking, but I think the name has changed. Anyway, it is just across the main road from the airport. You can drive into that lot and a lot attendant will ride over to the airport with you in your car, drop you off at curbside, and then take your car back to the parking lot. I don't know the daily cost, but it's about $8 or $9 a day.
I wish I could give you actual names and dollar amounts, but I just haven't really paid that much attention to the commercials. The signage in and around the airport is pretty good. You shouldn't have any trouble figuring it out once you see it.
Debbie