Determine the values of baseball cards by using a free valuation guide on a site such as FreeBaseballCardsPriceGuide.com or TuffStuff.com, as of 2015. It's also possible to appraise the cards online using the free service from JustCollect.com or the paid service from Beckett.com. Auction site eBay.com also contains pricing tools.
Both FreeBaseballCardsPriceGuide.com and TuffStuff.com offer an online directory of many different baseball cards along with details to help identify the exact year of publication and series to which the cards belong. FreeBaseballCardsPriceGuide.com organizes its listings according to decade, with entries for each team with cards for the years in that decade. The guide on TuffStuff.com is a free PDF that includes an index of cards per year and manufacturer. However, these guides may not receive frequent updates.
JustCollect.com offers a free service wherein you are able to scan your cards, or take a picture of them, and send the image to the company for a free valuation. It is also possible to mail cards to the store for a more thorough inspection. The Beckett.com valuation costs $10 per card, but provides and official certificate of appraisal that includes the price. Though auction site eBay.com does not perform appraisals, it does allow you to search for cards sold through the site to discover their exact sale price.