This Slashdot article on the new Gnome fonts from Bitstream got slightly off-topic on the subject of Arial/Helvetica vs its clones.
Ever wondered about the differences between Arial and Helvetica? That article points out the key means of distinguishing the two. Of course, the examples are at 72pt or such and I’m not sure I’d be able to spot the differences at a more common font size ;).
Another interesting site is Identifont. By answering simple questions, you can determine the name of a font by simply looking at it.
Tried Identifont. After twenty minutes of answering questions, it identified Helvetica Compressed as Aura.
The two fonts are fairly close, but they might of asked about the stem on the uppercase R. Aura is less curvy than Helvetica Compressed.
Anyway, cool tool; they put a lot of work into that. If all you have is a photo of the font and you need to match it, I can see it being useful. Thanks Mike.