WordPress 2.9 includes a really good basic image editor which can come in very handy. The image editor allows you to crop images, flip images and rotate them with ease.
To edit images in WordPress, click on the Edit Imagebutton when the image is uploaded. Once you do that a new Image editor will be displayed.
To select an area to crop, just click your mouse on the image and drag it as required, click on the scissor image to crop. You can also rotate and flip the image using the available buttons. Another interesting and useful function is the ability to undo or redo your changes.
The image editor allows you to apply the change to all the image sizes or just the image thumbnail.