A list of useful sites that provide free modules. List will be updated as and when I find new ones.
From Prestashop community
1) [Free module] display multilingual HTML texts everywhere
List of valuable and proven free modules for PrestaShop
1) Slideshow LITE
Description: This Prestashop free module display a simple slideshow on your homepage. Demonstration available on product page.
2) WordPress in Prestashop
Description: Module to display in a side block of your shop a customized list of the last articles from a WordPress blog. Best solution to easily create content for your shop and improve your SEO.
3) Newsletter block subscribers
Description: List, manage and export all visitors that have subscribe to your newsletter via the front-office block
4) Last customers block
Description: This module displays a block listing your last customers. Module parametrizable in your shop administration (format of each customer line, optional country flag)
5) PDF Invoice Plus
Description: Administration module to add a custom text (plain or HTML) at the bottom of all your PDF invoices or PDF delivery slips. It’s an easy way, for example, to add legal notes to all your invoices.
6) Shop Scheduler LITE
Description: There is a free version of this module Shop Scheduler LITE and a paid version Shop Scheduler PRO. This modules allows you to schedule the display of multi-languages HTML texts anywhere in your store. You can also copy complex visual items from your theme like column blocks, product pages tabs, … A must-have to communicate with your visitors: announce special operations, add visual elements or simply tell them you are on vacation!
7) Clean carts
Description: Clean unused carts from database to speed-up web pages display. Check carts contents using multi-criteria search (customer, amount, number of products, carrier, dates, …) Convert carts into validated orders to finalize orders in error (sometimes, bad validations could happen with payment modules)
8) Pack export
Description: The best pack to export your orders and customers datas as CSV files to be used in Excel.