And what do you already have?
I am about to buy a new lens for my New EOS 30D, but I am not sure on which one to buy.
A 50mm prime, dosen't matter at the moment what one, be it the 1.8 or the 1.4, Everyone should have a 50mm prime.
I found this comment appears quite often on TPF and I find it strange. If, for example, you shoot exclusively landscapes on a APS-c sized sensor, a 50mm is not really useful. I know it is cheap but what is the point if it is useless. Even if you don't shoot only with wide angles, I would find it useless as a walk around lens (as it is also often suggested). On a full frame camera this is probably the lens to have. For an APS-c sized sensor a prime in the 30-35mm focal range would be far more useful. To each its own, but I would think hard before buying a 50mm for a 30D. If on the other hand you shoot a lot of portraits with available light, a 50mm f1.4 and f1.8 will be ideal. Tell us what you need your new lens for.
I'm old fasioned, but that changes nothing IMHO. I learned on 50mm lenses, judging by the fact the OP stated "New EOS 30D" as well as the outward appearance that this is their first time buying a lens I am opperating on the assumption that this is this users first camera.
I'll admit, one has to shoot a crop body to truly understand a crop body, and I don't, and prolly won't shoot a crop body. Given that I am finding my self no longer using my 50mm primes in favor of my 85mm prime on my FF body for general walk about including some landscap work, I assume it's a still a safe bet to maintain the oppinion that everyone should have atleast one 50mm prime regardless of body early on in camera ownership, price has no baring on my stance in this. Given the affore mantioned assumption of first camera I find it a fairly standard thing that noobies don't yet know what they are shooting exclusivly, so unless otherwise stated I assume it's general use.
And even MORE importantly is that this person probably ALREADY figured something out considering this thread was made over 2 years ago!