First you have the official SolidWorks EDU Practice Excercises PDFs (WARNING: direct PDF link).This book has good beginner level things, and is free via Kindle Unlimited if you have Amazon Prime. 507 Mechanical Movements is a fun site to browse and try to model, especially once you start learning some of the more advanced mates. The monthly CAD challenges posted on r/CAD usually have a few beginner friendly things, and finally there is the ole "get an el cheapo caliber from Amazon or Harbor Freight and start going to town on stuff on your desk" approach. Pretty much all of these work and I somehow managed to list them in ascending order of difficulty kind of, but don't forget to use good modelling practices as well; test your models by resizing them, or modifying them in strange ways, and test yourself by learning to go back and fix what breaks when you do so. Learning what is likely to fail and how to repair it can seem difficult at first, but I probably learned more about how constraints work by abusing them than I ever would have by studying them (but you should totally actually study them, too).
How about these exercises? http://www.amazon.com/100-CAD-Exercises-Practicing-design-ebook/dp/B00TBYS84Q
You can check out these set of exercises you can practice with: http://www.amazon.com/100-CAD-Exercises-Practicing-design-ebook/dp/B00TBYS84Q
Also, there are good tutorials here: http://computeraideddesignguide.com/category/solidworks/