But I had a small epiphany as I was looking at
MMO-Champion and some of the beta changes that have been made for Cataclysm. (Yes... you could consider this a spoiler if you'd like.) And I came across the Multi-Tracking picture that they have. (Picture shamelessly stolen from MMO-Champion.) So, now that you can track multiple things at once you can gather even more as well.Most of the toons that I've leveled as straight gatherers for profit have learned skinning and mining. Leather from skinning is used by leatherworkers, and ore/gems from mining is used by jewelcrafters and blacksmiths. Your other option (which can also be quite lucrative) is herbalism, which the herbs can be used by alchemy and inscription.
Ideally, however, you would want to maximize your money by choosing both mining and herbalism. Well, unless you're okay with switching tracking constantly or using some mod like maybe Spotter (I have no clue if it still works or ever did, so I'm not linking it), you'll probably miss some flowers or mining nodes. So, with this new multi-tracking, you should be able to easily track both which means maximizing profit from gathering professions.
Just something to look forward to in Cataclysm if it makes it to live.