We have used copywork throughout our homeschool years as a way to not only have handwriting practice but also to expose our daughter to poetry, quotes from famous people, rights of a child and many other projects.
I have found that copywork has many benefits. It is independent work from the time a child is young, it is work that along with illustrations can be very satisfying and it gives a me an opportunity to reinforce parts of a book or subject we are studying.
I have made up our own copywork over the years using sites like this one. Sometimes I would skim the chapter we were reading in the morning the night before and find what I thought to be a key sentence/paragraph and use it. Many times I have used poetry or quotes. Sometimes I have used letters to Aunts and Uncles as a great way to encourage copywork.
There are many prepared copywork books and over the years we have used a few of them.
Queen Homeschool Supplies is one supplier of a variety of copywork books.
Simply Charlotte Mason has some free manuscript copywork materials.
If you would like some quotes for copywork take a look at WikiQuote. For poetry you can take a look at this page at Old-Fashioned Education. I especially like the book on this page Poetry Every Child Should Know.