Minimum System Requirements:

Windows XP/Vista
1GB System RAM (XP)/ 2GB System RAM (Vista)
2.4 Ghz Intel Pentium 4 or equivalent processor
Direct X 9.0c compliant video card with 256MB RAM (NVIDIA 6800 or better/ATI X850 or better)

Recommended System Requirements:

Intel Core 2 Duo processor
2 GB System RAM
Direct X 9.0c compliant video card with 512MB RAM (NVIDIA 8800 series, ATI 3800 series)

Supported Video Card Chipsets:

NVIDIA GeForce 200 series
NVIDIA Geforce 9800 series
NVIDIA Geforce 9600 series
NVIDIA Geforce 8800 series
NVIDIA Geforce 8600 series
NVIDIA Geforce 8500 series
NVIDIA Geforce 8400 series
NVIDIA Geforce 7900 series
NVIDIA Geforce 7800 series
NVIDIA Geforce 7600 series
NVIDIA Geforce 7300 series
NVIDIA GeForce 6800 series
ATI HD 4800 series
ATI HD 4600 series
ATI HD 3800 series
ATI HD 3600 series
ATI HD 3400 series
ATI HD 2900 series
ATI HD 2600 series
ATI HD 2400 series
ATI X1900 series
ATI X1800 series
ATI X1600 series
ATI X1300 series
ATI X850 series

While this does look modest compared to say Crisis. Keep in mind gamers will probably want to skip the minimum requirements and shoot for the recommended set to really enjoy Fallout 3 in all it's glory.

Fallout 3 is set to release on the PS3, Xbox 360, and PC in North America on October 28.