The Nintendo Wii was never meant to challenge the horsepower of other next-gen consoles and specs leaked over the web seem to reinforce that. They are of course unoffical so take with a pinch of salt, and they are certainly lower than I expected.

CPU
- Superscalar microprocessor with six execution units (floating-point unit, branching unit, system register unit, load/store unit, two integer units)
- Operating speed of 729 MHz
- Bus to main memory: 243 MHz, 64 bits (maximum bandwidth: 1.9 gigabytes/sec)

GPU (Hollywood )
- Operating speed of 243 MHz
- 3 megabytes of embedded graphics memory
- 24 megabytes of internal main memory
- Internal main memory operates at 486 MHz
- Maximum bandwidth between GPU and main memory: 3.9 gigabytes per second
- The GPU of the Wii is identical to the GC's but it is on average 1.5X faster

Other details
- 64megabytes of GDDR3 external main memory
- Internal non-removable 512MB flash memory used as storage for game save data and downloadable content
- The following interfaces are included with the Wii: SD card slot, Wireless controller, two USB 2.0 ports, wireless LAN, 4x GC controller ports, 2x GC memory card slots and an AV multi output jack (analogue only)
- Two main disc types supported the single sided 12cm single sided 4.7gb and the double sided 8.51 GB. Nintendo GC discs also supported. The maximum read speed is the equivalent of a 6 speed DVD

Thanks Inq, and more specs at Spong