There are many great websites which offer free guitar tabs and other guitar learning resources which will help supplement your lessons, below are a few of these sites to check out.
This website has one of the most comprehensive collections of Tabs on the internet
The Fender online tuner is great to use if you're caught short without a guitar and you have a computer or phone at hand
Metronomes are great tools to use while practising as they help to develop your consistency, timing and your speed
Backing tracks are also a great tool to use while practising as they help you to simulate playing along with a band, this site has thousands of free backing tracks to have a play along to
Both of the sites above offer sheet music for thousands of pieces specialising mainly in classical and flamenco