Light, Flooding In... How?

Swift

<div class="IPBDescription">(oh.. uh.. hl2...)</div> <a href='http://img61.echo.cx/img61/7329/how0xh.jpg' target='_blank'>http://img61.echo.cx/img61/7329/how0xh.jpg</a>

Light.. flooding in.. .. pretty.... how?

Huze

There's a model called "models/Effects/vol_light.mdl" that might be what you want.

Merkaba

[Edit -Oops, I thought you were just editing for HL using the source editor.]
Go into your texture browser and do a search for 'fade' textures...there will be ones which are yellow/blue and fade into blackness. Apply that (or your own texture which fades to black) to a brush where the light will be, rotating the texture appropiately, and then tie the brush to a func_illusionary with render mode additive and FX amount somewhere between 0 and 255. Use the NULL texture on faces which will be blank (ie the top/bottom faces)

Surplus info:

Additive render mode on brushes/models will make black areas appear invisible and fade in to the lightest areas, allowing for some really cool effects (eclipse's scrolling electricity, 'overlays' which are used to make parts of a texture light up (do a tex search for 'fx' - these are all to be used in conjunction with their matching non-fx named texture), and many more effects seen in NS levels.