Summertime is the perfect time to learn a few pop and rock grooves and licks! Even during the school year, I hop onto Youtube to listen to a few grooves for piano or cajón for choir. Here's a place I found recently.
Willie offers online lessons but he also has some free video tutorials on his website and his Youtube Channel.
Check out Rock Groove #2. It's pretty neat:
I like how he gives you ideas to vary the pattern.
Give it a try! Have fun.