A mitosis worksheet with an answer key is available at Biologycorner.com as of September 2015. It doubles as an Internet lesson that can either be completed online or downloaded and printed out for students.
Most mitosis worksheets and answer keys are formatted as .pdfs or .docs, but a few can be found online in full HTML form, which eases downloading for those who don't have .pdf or .doc readers installed on their computers. One such HTML formatted sheet is available at Biology Corner. It can be printed out or completed by students online. Most similar websites require users to sign up to see the full answer key or to email the website for the answers.