One of the more popular free IPA download sites, PandaApp requires you to sign in with either your Facebook account or you could register yourself on the site. The only downside is that they host their IPA files with a website that limits transfers to 2GB a day, but that is plenty for most people.
With a clean and straight-forward user interface, iOSNinja provides you with numerous iDevice resources from firmware files, jailbreaking wizards and tutorials to a huge collection of regularly updated IPA files for free download. Therefore, you must be using an Apple device running a jailbreak to install the free apps from most of these IPA download sites using Cydia Impactor. These listed sites are for IPA stores iOS which has very strict rules regarding downloading and installation of apps on your iPhone, iPad or iPod touch from third-party providers and sources other than iTunes and the AppStore. Interestingly, even after sometimes taking the plunge and shelling out the money for an app you require, you often find yourself tied down with pesky subscriptions.
Many people for the day when AppStore offer a free trial version for a paid app that you think you require, before you can spend your hard-earned cash knowing that the app does work as advertised.