PTHPasteboard Pro is yet another multiple clipboard manager, but this one has a cool little trick up its sleeve: text filters. In addition to saving clipboard history like the many other clipboard manager out there, PTHPasteboard Pro allows you to use 40+ text filters to manipulate and transform the clipboard text. For instance, you can create filters that change the case, wrap and unwrap lines, use smart quotes, etc. Furthermore, you can apply these filters sequentially to achieve some complicated effects (check out the screencast to get a better sense for what you can do). Especially used in sequence these filters can be quite sophisticated, like a less powerful TextSoap or BBEdit Text Factory. The Pro version also offers clipboard syncing across different Macs on the same network.
PTHPasteboard Pro is $19.95 and a demo is available. There is also a free version (minus the Pro) that offers just clipboard history without the text filters