Skinning and mining is good. They can be profitable. There is also herbalism. People need plants. :D
Another thing you could do is pick up blacksmithing to make armor for yourself. Or, you can just do two gatering professions so that you can acquire more money and earn your level 40 mount and riding skill, along with each even levels spells along the way.
Plus, if you stick with this method of money you can afford upgrades of armor from the Auction House (you probably won't want and/or need to do this until 60. Even then, there are raids). You can also save up and earn your level 60 mount and riding skill sooner. Unless, that is, you do BGs (30 tokens of each AV, AB, and WSG) for your mount. Even if you choose this option though, you will still have to buy the riding skill.
Good luck!