There are a number of options for selling NASCAR collectibles including selling at collectibles shows, selling online, and selling through local advertisements. The best option will depend on the nature of the memorabilia and how much there is to sell.
Finding a collectibles show in the local area is a good option for selling a large quantity of items at once. NASCAR memorabilia is sold at general "sports collectibles" shows, but there are also shows that are specific to NASCAR items. Selling at a show requires renting a space where the table or booth can be set up, and that may require reserving a spot in advance. This is true especially if it is a popular show.
Selling online is a good option for items that are small and inexpensive to ship. Some popular online sites to list merchandise are eBay, Amazon and Bonanza. While known for conducting virtual auctions, eBay also allows selling at a fixed price. Amazon requires sellers to set a fixed price, and the merchandise must also have a bar code number such as an ASIN, UPC or ISBN.
Options for selling locally include listing the items on Craigslist, selling items through ads in local papers, or putting the item up for sale in the Penny Saver or local equivalent.