WordArt.com is a great online word cloud creator that enables you to create unique word clouds. You can customise every bit of your word cloud art, including words, shapes, fonts, colours and layouts.
It's great fun experimenting with shapes and colours. You just click 'visualise' to see the results and download the image. It's really simple and free (we like free!). You can pay for a higher quality image for printing, but the free images are fine for blogs and websites.