From this page you can download the EAP builds for ReSharper 3.1. If you are looking for the latest released version, visit ReSharper download page.
Pre-release software. Quality is not guaranteed
This is preview software aimed at providing you with an opportunity to test the newest features of the product being under development. JetBrains does not guarantee that this software will run trouble-free. Using this software is at your own discretion and does not entitle you to any customer support.