Alrite, here we go. I've taken the liberty to test out some of the newest games (and older games too) and I hope that everyone can use these for their base reference. I've included OC'ed bench too.

*Note: Just in case some of you are wondering, some of the games are borrowed. I do not own all the games. I hope that every Inspiron 1520 can contribute to this list as a base reference.

@alex, maybe you should put this list in the front page for future ref. Thanks.

Specification: Intel C2D T7250 2.00GHz, 2GB DDR2-800, 256MB NVIDIA 8600M GT, 250GB Hitachi SATA 5400RPM, Windows Vista SP1, Forceware 180.84.
Note: OC'ed NVIDIA 8600M GT is clocked at 650/1300/550.

3DMark 2006 (1280x800; Default Settings; PhysX in Control Panel OFF):
Default: 3649 3DMarks
OC'ed: 5019 3DMarks
*Note: PhysX is turned oFF because it will cause the GPU to throttle to 2D Clocks if enabled. Not sure why this happens though.
*Note: If I have time, I'll tryout Vantage.

Dead Space (1280x800; Max Settings; Vsync OFF) Measured using FRAPS.
Default: Min 23FPS; Avg: 31FPS; Max: 40FPS
OC'ed: Min: 32FPS; Avg: 44FPS; Max: 50FPS
Maximum measured temperature: 78°C for CPU, 72°C for GPU
*Note: Vsync causes the game to capped to 30FPS. I don't think Vsync is required since it already runs below 60FPS.

Counter-Strike: Source Video Stress Test (1280x800, Max Settings, 4xAA, 16xAF)
OC'ed: 133.84 FPS
Default: 96.65 FPS
*Note: Video Stress Test is not a good measurement if compared to practical gameplay session.

Counter-Strike: Source 16 Bots (Same settings as above)
Default: Min 35FPS; Avg 57FPS; Max 68FPS
OC'ed: Min 44FPS; Avg 65FPS; Max 84FPS
Recommended Settings: 1280x800, Max Settings, 2xAA (4xAA if overclock), 16xAF
*Note: Minimum FPS happens when there are heavy actions. If you're playing in a server less than 16 players, then you can go for 4xAA without OC.

Need for Speed™ Undercover (1280x800, Everything High, No AA, No AF, Reflection On)
Default: Min 22FPS; Avg: 27FPS; Max: 34FPS
OC'ed: Min 25FPS; Avg: 30FPS; Max: 42FPS
Recommended Settings: 1280x800, Everything on High, Shadows OFF, No AA and AF, Reflection OFF)
*Note: Maximum measured temperature: 61°C for GPU

Crysis® (1280x800, Custom Config, Shadows OFF, Godray ON, No AA, No AF, Volumetric Effects OFF, Motion Blur OFF, HDR ON, Default view distance, DX9-codepath, SSAO OFF, LowSpec Texture (Not enough VRAM))
Default: Min 24FPS; Avg 32FPS
OC'ed: Min 27FPS; Avg 36FPS
*Note: It's very playable with the custom config. And definitely I think the GodRay is a better choice than enabling shadows.
*Note: Maximum observed temperature is 77°C.

Unreal Tournament III Deathmatch 7 Bots (1280x800, Sliders on 5, Hardware Physics OFF, FOV 100)
Default: Min 26FPS; Avg 36FPS
OC'ed: Min 34FPS; Avg 45FPS
Recommended Settings: 1280x800, Sliders on 4, Hardware Physics OFF, FOV 100 (Widescreen)
*Note: Since this game uses Unreal Engine 3, the setting and performance guideline can be used for Gears of War too. Remember to turn off PhysX for this game too. It will likely to take up the resources of the graphic card if enabled.

Command & Conquers 3: Kane's Wrath (1280x800, Settings on High, Shaders Ultra High, Shadows Ultra High, No AA, No AF)
Default: Min 24FPS; Avg 27FPS; Max 30FPS
OC'ed: Min 29FPS; Avg 30FPS; Max 30FPS
*Note: This game has a frame limit of 30FPS. Therefore, the max FPS is 30FPS only.

Fallout 3 (1280x800, Custom Config, Lowest view distance, Shadows ON, HDR On, 2xAA)
Default: Min 31FPS; Avg 39FPS
OC'ed: Not tested
*Note: I don't have the game with me now. So, I forgot the custom config settings.