reviving cast iron

Two ideas: for sandblasting, speak to a local cemetery monument sales rep. They have traveling sand blasted come through to encsribe stones regularly.
Also, a local "old-timer" suggested "Naval Jelly" to remove rust. I purchased some and it does! It is sold in hardware stores and the brand is called "Loctite". Or look online at www.loctiteproducts.com under products and where to buy

Thanks for all the responses! I thought that I was doing a search for previously posted items, I had no idea I would get such prompt and great answers. I would have specified more if I had known. I have some pieces that are not rusted, but they have a sort of build up of crud, not a smooth surface. I had seen a post on some site somewhere, where someone stated putting their cast iron skillet in white vinegar for a time, checking often of course, and the vinegar sort of "ate" through the build up of crud. I did think of the sand blasting too, but wondered if it would be costly, and if they would think me a bit wierd!

You can also use a wire brush attachment for a power drill.

I've sandblasted one, too. And that probably is best, since it will leave the surface slightly pitted, as when cast (they are cast in sand). However, you could get some heavy 'grit' 3M Scotch-Brite at Home Depot (or where-ever – look for the burgundy colored stuff), and use some serious elbow grease and a little Bar-Keepers Friend.

Season by coating lightly with vegetable oil (canola, grapeseed) and baking in the oven at no more than 325 degrees for an hour. Wipe again, cool, wipe again & repeat, and so on. I'm big on threes, so I like to do this 3 times. It is a good idea to heat the pan on the stovetop to dry after each washing, and wipe down with a little oil each time to prevent oxidization due to atmospheric moisture – or if you are like me and store them on the stovetop (on the wacky, and rarely used mini-burner), to protect them from random splatters. Never leave unwashed long, and get acidic food out quick, or not only will it undermine your season, the food will start to taste like iron filings.

Wow, that's impressive -- sandblasted! If it's not quite that bad, a good elbow grease session with some steel wool to scrape off the rust should do it. Then it's a just a matter of reseasoning it -- here's our video on how:

http://food52.com/blog/3547_how_to_season_cast_iron

Can you give us some specifics? I have some old pieces I found at the grandparents barn that were totally rusted. I took them to a local autobody place and had them sandblasted. Of course they needed reseasoning--but the surface was smooth.