Give is the best FREE WordPress plugin that will allow you to collect donations online. The plugin integrates well with PayPal.
Give is the highest rated, most downloaded, and best-supported donation plugin for WordPress. Built from the ground up for all your fundraising needs, Give provides you with a powerful donation platform optimized for online giving.
Transform the way you accept online donations. With Give you can accept charitable gifts through customizable donation forms, view donation statistics and reports, manage donors, and integrate with a wide variety of third-party gateways and services.
To download Give, head over to your WordPress Admin Area/ Plugins and Add New. Search for Give and install.