Here are some of my current favorites.
1. What do you need your clipart for?
Clipart to be used on your website or blog can be in color while the clipart used in printed materials may need to be black and white images. Clipart that was designed to be black and white is generally preferable to printing color images in black and white.
2. Can’t I just use images from other people’s sites?
I know people like to enter search terms and then just click <images> on Google and swipe images but it really is important for you to make sure that you are using your images within the standards of both copyright and polite usage. If you want to use a picture that someone made for their own site, you need to purchase it from them. If you use an image from wikipedia, it will tell you what rights you have to use it. And if you choose an image from a dedicated clipart site, you need to use it within their parameters.
3. My links:
Microsoft Halloween clipart Microsoft clipart is available to anyone who owns a copy of Microsoft Word. They have 66 pages of Halloween clipart that you can use for whatever purposes you wish.
Classroom Clipart is a site that allows you to download as many pictures as you wish with a free membership. They have an enormous collection of clipart, Classroom Clipart offers pictures that are suitable for children.
Harry Potter Graphics This is a small collection of clipart. The artist requests a link back to the site if you use them. That is usually a good idea anyway.
FG-A Halloween Clipart has lots of bouncing pumpkins and jack-o-lanterns, but the art is a little cooler than you are used to.
The Kidz Page has some really interesting art that appears to be three dimensional.