Depending what kits they are, I might be interested. Other than myself I'd say eBay would be the best way. Lots of people check that out on a daily basis to see if they can score a great deal. And as long as you start off with a fair price (whenever I sell something on eBay I start the bid at 3/4 the price I paid or value of it) it should sell quickly.
Stuart_Canada,
I didn't know hoyardsale existed, thanks for informing me for that. I haven't seen anything on there that suits my needs currently but possibly there will be something in the future.