I'm not realy using it much but i2p[0] has been around for a while. It's Java though as all other projects like this in case you have anything against it.
IIRC the main issue with I2P is that it doesn't natively offer access to traditional websites the way Tor does. You can configure your browser to connect to a remote HTTP proxy over I2P and access the web that way, but that requires you to find such a proxy first (preferably several such proxies, each with multiple users, so that your traffic across multiple sessions can't be correlated by using the outproxy IP), and setting it up is a lot more complicated than Tor's method of "download Tor browser, click run".