Transcend have just announced some 1GB DDR2-533 Micro-DIMMs which are designed in such a way that they're only 65% the size of a regular SO-DIMM.
Head over to Transcend's website for more info on them.
Transcend's Micro-DIMMs use the latest 214-pin "mezzanine connector" technology, which reduces the size of the module by approximately 40 percent when compared with an SO-DIMM. Transcend's 256MB to 1GB DDR2-533 Micro-DIMMs improve performance considerably and increase your system's overall stability. All of Transcend's DDR2-533 memory modules follow the standard developed by JEDEC (the Joint Electron Device Engineering Council), the memory industry's standards organization. Using a Transcend DDR2 Micro-DIMM module in your Notebook will provide you with significant benefits, including lower power consumption, which can improve battery life and help achieve better overall performance.