The 802.11g specification was ratified by the IEEE in 2003. 802.11g uses the OFDM encoding of 802.11a in the 2.4 GHz band, and also falls back to DSSS to maintain backwards compatibility with 802.11b radios. This means that raw speeds of 54 Mbps (20 to 25 Mbps data) are achievable in the 2.4 GHz band, all while keeping backwards compatibility with existing 802.11b gear. This is a very promising technologyso promising, in fact, that the lack of ratification didn't stop some manufacturers from shipping gear that used the draft standard, even before it was ratified. In addition, those same manufacturers continue to push the envelope with development of proprietary extensions to 802.11g that can double raw speeds to 108Mbps and faster.
If you are building a network from scratch, strongly consider the benefits of 802.11g. It allows existing 802.11b users to continue to use the network, while providing a significant speed boost for 802.11g users. 802.11g is a massively popular technology, as it provides many of the advantages of 802. 11a without significantly raising cost or breaking backwards compatibility. Since it offers many advantages with relatively few drawbacks, it is already the next massively ubiquitous wireless technology.
Bluetooth, Mobile Phones, and GPS
Network Discovery and Monitoring
Wireless Network Design
Appendix A. Wireless Standards
Appendix B. Wireless Hardware Guide