We recently posted a plug-in for Mac OS and registry keys for Windows allows you to save large PSD and PSB images in Photoshop CS5 without compression. The resulting size of your image is much larger. However, saving the file can be much faster (20x in some cases), if you have a fast hard disk and enough disk space to hold the larger file size.
Get more information and download the plug-in and registry keys from the following knowledge base document:
Mac performance guru Lloyd Chambers discusses his benchmark findings in the following article on his blog: