PhotoFreebies is a collection of free plugins for performing useful photo manipulations and effects like sepia effects, saturation gradients, b/w conversion, color space transformations and many more. Some of them have a dialog with adjustable controls whereas others are applied instantly without displaying a dialog.
PhotoFreebies works in dozens of graphics applications including Photoshop, Paint Shop Pro, Photoshop Elements, PhotoPlus, Photo-Paint, IrfanView and PhotoImpact under Windows and MacOS X. The plugins also run natively in Photoshop CS3/CS4 on Intel-Macs. There is also a 64bit version for the 64bit version of Photoshop CS4 for Windows.