If you don’t have time to visit the CamelCamelCamel website, you can install its add-on for Chrome and Firefox, called The Camelizer (uk.camelcamelcamel.com/camelizer). Just click its toolbar button when you’re viewing a product page to see a price-history graph, which also includes data for third-party sellers, and to create a price watch for that item.It can be difficult to decide on a starting price for items that you sell on eBay -set it too high and you might not attract any bids, but start too low and you won’t make much profit. You can get a rough idea of how much the product usually sells for by searching for it on eBay and selecting the ‘Sold listings’ option on the left-hand side of the results page.To find out if now is the best time to sell or buy a specific item, look it up on Bidvoy (uk.bidvoy.net). This brilliant site tells you the average price products are selling for, so you don’t ask too much or too little for yours. It even tells you which times of day and week are the most lucrative to sell items and the cheapest to buy them, and whether you’ll get a better price on Amazon.Bidvoy presents its data as a line graph that shows the final prices of eBay auctions and buy-it-now sales over the last six months, so you can easily spot trends and see whether the value of the item is rising or falling. It also provides a sample of current listings for that product and tells you whether they’re over- or under-priced. This graph (below) suggests that now would be the worst time to sell a 16GB iPhone 5C, because it’s going for more than £60 less than its average price and £92 less than its peak price.Although paid-for apps for your phone or tablet cost a few quid at most, you can save money by waiting for time-limited discounts or for the apps to go completely free. To track the prices of iPhone and iPad apps, visit the Price Drops page at AppShopper (appshopper.com/prices). This lists all the most recent price changes for iOS and lets you click straight through to the iTunes store to buy each newly discounted or free app. When we visited, bargains included Video Downloader Pro (free for one day, usually $3.99) and finance app Saver 2 – Money Manager (now free, was $4.99). Add apps you want to your Wishlist and you’ll be notified as soon as their price drops, or follow AppShopper on Twitter for news of the latest discounts.For Android apps, the Price Reduced page at AppBrain (bit.ly/appbrain374) works in the same way as AppShopper, but each app is also given a rating out of 100 from the AppBrain team. You can filter the list to show only apps from a specific category, those that are ‘hot’ today or this week, or the most popular discounted apps in the UK. There’s also a free AppBrain App Market app, called Apop (bit.ly/appbrainapp374) that lets you find bargains directly from your mobile device. Pick of the bunch at the time of writing was the comprehensive football results and statistics app Ultimate Premier League 15/16, reduced from £9.99 to 99p.The excellent ebook-deals website eReaderlQ (uk.ereaderiq.com) has a comprehensive Popular Price Drops page (uk.ereaderiq.com/drops) that shows you which books are now available for less or for free in Amazon’s Kindle store. You can filter these by minimum discount, maximum price, genre, length and other useful criteria, then click the Track It button to be notified by email when the price changes again. Usefully, eReaderlQ lets you import your reading wishlist from Amazon, and also provides a price-history chart and summary for each title, so you can see when it was most and least expensive.The cost of air travel can vary wildly depending on the time of day, week and year that you book your flight. Fortunately, there are several useful tools for tracking airfares, of which our favourite is Skyscanner’s Price Alerts feature (bit.ly/skyscanner374). Simply search for a flight, specifying exact airports and dates, then when the results appear, click the Get Price Alerts button in the top-left corner. Skyscanner will monitor fares from dozens of airlines every day, and email you as soon as prices drop (or rise), so you can book your seat while it’s cheap.Alternatively, you can decide when to take your holiday based on the least expensive time to fly by selecting ‘Cheapest month’ in the drop-down Depart menu on the Skyscanner homepage. When the calendar appears, switch to Chart view to see the cheapest days in the cheapest month to fly out and return.The price of digital games changes from store to store, and from week to week, with special offers and bundles often significantly reducing the amount you pay for a specific title. Make sure you don’t get ripped off by using lsThereAnyDeal.com (isthereanydeal.com) to compare current and past game prices from sites including Steam, GamersGate and Origin, including the lowest recorded amount for each title. If there’s a particular game you want to buy, you can set a maximum price and add it to your ‘waitlist’ to be notified of any drops. lsThereAnyDeal.com also rounds up vouchers, time-limited discounts and bundle deals, so you never pay full price for game again.For console games (and the consoles themselves), you can use the Price Watch tool at Game Crawler UK (bit.ly/gamecrawler374) to discover the best place to buy from as soon as the price comes down.