Rumors about TiVo's "coming soon" 802.11g support have recently come true. The Houston Chronicle has a short article about two 802.11g adapters for a TiVo running software version 7.1 (Netgear's WG111 and D-Link's DWL-G120).
The support page for TiVo Wireless Adapters confirms that these two wireless adapters will work with your TiVo in wireless G mode, as long as it has the most recent 7.1 OS release. This should make show transfers go a lot faster. [thanks Mike!]