Onion.ly is described as 'Access the Tor and I2P networking without leaving your favorite browser' and is an website in the Security & Privacy category. There are more than 10 alternatives to Onion.ly, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac, Android and BSD. The best alternative is Tor Browser, which is both free and Open Source. Other great sites and apps similar to Onion.ly are Tor (Free, Open Source), Freenet (Free, Open Source), I2P (Free, Open Source) and Orbot (Free, Open Source).
The Tor software protects you by bouncing your communications around a distributed network of relays run by volunteers all around the world: it prevents somebody watching your Internet connection from learning what sites you visit, it prevents the sites you visit from learning...
Tor is free software and an open network that helps you defend against traffic analysis, a form of network surveillance that threatens personal freedom and privacy, confidential business activities and relationships, and state security.
GNUnet is a framework for secure peer-to-peer networking that does not use any centralized or otherwise trusted services. A first service implemented on top of the networking layer allows anonymous censorship-resistant file-sharing.
FreePN is the first completely free, completely open network dedicated to protecting your online privacy. Joining the network is easy: just download and install the app. No accounts, no registration, no setup. Once you start the app, you're already protected.