Various lab protocols I've written up over the years.

• Osmotic Shock [PDF] - a protocol for releasing the periplasm of E. coli by osmotic shock, based on the methodology of Neu & Heppel. This protocol assumes there's a reason your protein should be in the periplasm to begin with (e.g. pelB signal peptide). Periplasmic expression tends to have a lower yield than cytoplasmic expression, but the periplasm is an oxidizing environment which can be important for getting a protein with disulfides to fold correctly. Also, the periplasmic fraction after osmotic shock is much cleaner than a cytoplasmic prep, so if you're doing high-throughput screening, are content with a semi-pure prep, and don't want the hassle of an additional step of purification, periplasmic expression may be the way to go.
• Site Directed Mutagenesis [PDF]. This is similar to the commercially available QuickChange® kit from Stratagene, although it should be a heck of a lot cheaper and I think it works better.
• Generic PCR protocol [PDF].
• Solutions [PDF] - formulations for various solutions/media that I use.