If you click Spells at the top of the page, then Spellbooks, you'll find each of the covens on this site has their own spellbook composed of spells their members have posted on the site.
I've found it's easier to find things through just the Spells section, but that may just be me. I hope this helps.
Nothing good is free. If you are looking for someone else's work as inspiration there are many places to try, this forum has several such topics. If you want a blank book to write your own spells in you are probably gonna have to pay for it. If you want a spell book that someone else wrote to work from, well your gonna pay for that too and not just with money. Most people will share a few spells some may even share the whole book but you run the risk of getting some horrible information out of it.
The best spell book for any magic user is the one that user makes themself
I agree with PaganStar.Write your own spells. It is personal and fits you. They are going to be the ones that work best for you.
If you need a to look at other's spells, there are many book of shadows published out there. Also, some beginner's books on magic have some sort of small spell book in the back of it. If I am not mistaken, Scott Cunningham's Wicca: A Guide to the Solitary Practitioner has a small BoS in the back. I believe True Magick by Amber K. also has some spells at the end.
Just keep reading and working on the basics. Don't rush to cast that first spell. I personally did not do any spell work until I was about 3 years into my practice.