Beckett offers a subscription-based price guide for Pokémon cards along with up-to-date information. In terms of free services, Pojo and RarityGuide both offer price lists, but these sites do not state how often the included prices are updated.
Online card databases often include information on the different versions of cards, such as 1st Edition or Unlimited, giving prices for both. Pojo and Beckett both produce lists in numerical order and sort by set. RarityGuide uses a search feature and arranges the cards by alphabetical order. It also features a "Rarity" field that estimates the demand for cards on the secondary market.