Available for Android and iPhone as of today, Yahoo AppSpot (download: Android | iPhone) recommends new apps to download based on the apps you already have and the apps you've searched for in the past. It's a great way to discover new downloads when you don't necessarily want to peruse the hundreds of thousands of listings in the Android Market or the Apple App Store.
For each user, AppSpot provides a personalized daily serving of app recommendations. Trending apps on the Web have the most weight in determining what it serves up, while installed apps and any app-related queries made through mobile Yahoo search or through AppSpot itself factor in as well. And to avoid returning irrelevant results, AppSpot also uses your geo-location as yet another input. It covers 20 categories including News, Sports, Entertainment, and Productivity. And for each of its recommendations, it provides the app's name, description, ratings, price, screenshots, and a link to the download page. There's also a built-in search function, which gives you instant results as you type. It's a nice touch, considering we don't always know exactly what we're searching for.
Overall, we like the idea behind Yahoo AppSpot and found it to be a nice tool for discovering interesting and personally relevant apps. However, it is worth mentioning that AppSpot's user interface needs some work. The browsing experience can get tiresome. With a Home screen that displays only three columns at once, it's a bit of a pain to swipe through to see all 20 categories. Also, within each column, only three out of AppSpot's four recommendations can be seen above the fold, which means you must swipe up to see the fourth. And doing so for 20 different columns can get annoying, to say the least. That said, we'll be waiting for the next iteration.
Side note: Yahoo also released a desktop tool called App Search, which essentially does the same thing, but without the daily recommendations.