After collecting '60s music and memorabilia for three decades, René Klaassen is using eBay to turn all those memories into money. Key to his efforts are market research tools that help him determine what's likely to sell and for how much, what the best dates and times are to list certain items, and other valuable information.

Case in point: a Pink Floyd 45 rpm record he recently decided to part with. "I didn't know what to expect," says Klaassen of Los Angeles. "I was hoping for something in the hundred-dollar range." Typing "Pink Floyd" into a market analysis tool from Terapeak revealed to Klaassen that Sunday listings did better than Tuesday listings, listing an item at 10 a.m. beat listing it at 5 p.m., and 10-day auction-style listings fared better than those lasting only seven days.

Klaassen (eBay User ID: heineken) fine-tuned his listing accordingly. The result: He sold the record for $285. "It's quite nifty," Klaassen says of his market-research capabilities. "Rather than just grabbing an LP or 45 off the shelf [to sell], I immediately go to Terapeak and look for sales history."

Similar market research tools, both from eBay itself and from third parties that license data on sales closed on eBay, can help many businesses on eBay outperform expectations. Victoria, British Columbia-based Terapeak starts with data licensed from eBay and allows sellers and buyers to conduct research such as looking back at completed items over extended periods of time to find price trends for specific products. "If you sell Nike Air Jordans on eBay, you can go to www.terapeak.com, type in 'Nike Air Jordans,' and find out how they have been doing [over] the past 30 days," says Dave Popowich, Terapeak's marketing coordinator. The online subscription service costs $16.95 per month and provides trend data going back as far as a year in some cases.

HammerTap's DeepAnalysis market research software runs on a user's own PC. For $17.95 monthly or a $179.95 annual license fee, HammerTap can do a number of powerful analyses, such as studying how starting prices relate to bids and determining which category is best for an item based on the number of bids or selling prices in different categories, says Jen Cano, director of PR at the Orem, Utah, company.

Other popular research tools come from ándale, a Mountain View, California, company whose products help eBay sellers identify what's been hot in the past six weeks, determine prevailing selling prices, count the number of sellers of specific items and more. ándale's $7.95 per month Research tool even gives users recommendations on such crucial criteria as the price, category, day and time for a given listing.

The new kid on the block is eBay Marketplace Research. John Bodine, eBay product marketing manager, says, "Marketplace Research can help you understand sales and price trends within categories, as well as provide insight into new products you may wish to source and sell."

Specifically, Marketplace Research provides consolidated metrics on up to 90 days of completed listings. That's a considerable improvement over the previously available eBay completed listings information, which only showed 15 days' worth of data.

Marketplace Research allows for more sophisticated analyses of long-term data. Users can, for instance, see how completed listings of collectibles related to the Chicago White Sox Major League Baseball team rose steadily until the end of the 2005 World Series, then, following the White Sox victory, fell sharply. Those kinds of insights can help a seller decide whether to sell White Sox-related products now.

Marketplace Research is priced in three tiers. Fast Pass is designed for the casual user, who will pay $2.99 for two days' worth of unlimited access to the subscription services. Fast Pass users can tap into 60 days of historical data and see an item's average sold price, sold price range, average Buy It Now price, Buy It Now price range, last sold price, number of completed items and other metrics. Basic level, at $9.99 monthly, offers additional metrics, such as information on an item's start price range, number of successful sales and average shipping costs. Both the Fast Pass and Basic packages allow users to save up to 10 searches. At $24.99 a month, Pro level allows users to search 90 days of historical data, save up to 100 searches and research international data. It also includes more charting options and advanced filters. All three provide information on the top searches performed by buyers on the site.

The world of market research on eBay has come a long way in a short time, and it's still evolving. One significant limitation is time. For example, eBay Marketplace Research is initially limiting its data to 90 days, Bodine says, in part because of the massive computing power required to analyze millions of daily listings over a long period. However, given the annual cycles on which many businesses live and die, year-long market trends are of vital interest.

Even with their limitations, market research tools are well worth the cost to most sellers, who find that using them often results in faster sales at higher prices. "Prior to Terapeak, I didn't have a way of seeing what the market could bear," says Klaassen.

That cuts both ways, Bodine notes: Market research makes eBay more useful for both vendors and purchasers. "Research before you buy," he says, "and research before you sell."

Mark Henricks writes on business and technology for leading publications and is author of Not Just a Living.