Have a look at this picture of mine:

http://www.renderosity.com/mod/gallery/index.php?image_id=1592810

The green "Matrix"-style text in the foreground is a real 3d object, rendered in the scene by Poser.  As you can see, it contains opaque areas, transparent areas, bits in between the two and also casts shadows.  It is in fact very easy to do.  In your favourite art programme, create your text in whatever colour you like (in this case, bright green)., call this your "texture" image.  Then make an otherwise identical version where the text is white on a black background, call this an "alpha" image if you like; in the render, it will make your texture image transparent where the alpha is black, and solid where it is white, and will vary the transparency (as can be seen in the sample image) where the alpha image is grey. 

In Poser, create a flat square primitive, apply your "texture" image as the er, texture, and set your "alpha" image as the transparency map (Another way to do it would be to use the "alpha" channnel to cut through a solid colour/texture).  Press render and away you go - a text object.

My self-build system - Vista 64 on a Kingston 240GB SSD, Asus P5Q Pro MB, Quad 6600 CPU, 8 Gb Geil Black Dragon Ram, CoolerMaster HAF932 full tower chassis, EVGA Geforce GTX 750Ti Superclocked 2 Gb, Coolermaster V8 CPU aircooler, Enermax 600W Modular PSU, 240Gb SSD, 2Tb HDD storage, 28" LCD monitor, and more red LEDs than a grown man really needs.....I built it in 2008 and can't afford a new one, yet.....!

My Software - Poser Pro 2012, Photoshop, Bryce 6 and Borderlands......"Catch a  r--i---d-----e-----!"