I LOVE ZENTANGLES! I got hooked last year when I saw my 5th grade students doing this activity in art class. I went home, GOOGLED it and have been hooked ever since.
A great place to find patterns is TANGLE PATTERNS.COM! I also got tons of visual ideas after I GOOGLED and clicked on images.
There is a starter kit you can buy, but what I found, that works best for me, is a spiral bound sketch book, to keep all my projects and ideas in one place.
I did buy the fancy pens...
I got a lot of ideas from the following books:
I bought these templates to create the perfect outline shapes I wanted. I use the circles the most.
Here are some pictures of some of my favorites that I have created: