Same issue; once you've bought and learned mounts, got the bank slots and big bags, gold is pretty useless to f2p. Items mentioned are a useful sink for gold (I used to pile up walnut stock, and still do for all but one alt).
Now, as one alt got to Outland (Blingtron party teleport), I shuttle this one back and forth from Azeroth to Area 52 buying up fel iron bolts, casings, explosive, adamantine frames and to Stormspire for similar, plus major protection potions (all have limited availability, and I think most stack to 200). At worst you can vendor these back for 25% of what you paid, but if I eventually stop being f2p, each auctions for a few 10's of gold. Too low level to do anything much in Outland except explore (and die) and fish (and die).
I have to note that I now have the problem of several alts being 'full'; all slots contain items that will AH for 1000 g upwards, and having to selectively vendor these for a few measly silver. Can't even give gold or items away!
In case you've not found the trick, you can save trogging back and forth to a specialised vendor every few quests due to 10g limit: Sell back 4 walnut stock to an engineering vendor for 25% of its cost, and use the money to buy more walnut stock. Repeat up to 10 times, or as much as you feel comfortable (actually, you could sell back 8-9 pieces to increase the gearing). When you get money from quests, you can then buy back the walnut you sold from any vendor. BUT; do NOT logout; and be very careful selling ANYTHING whilst you walnut stock is on the buyback list - you risk bumping it off the list. I particularly use this during Darkmoon, as just having a bit of walnut to buy back saves you having to return to base and then back to the Island.
If anyone has a solution to (f2p) transferring an excess of gold or items, happy to hear it: I'd gladly hand over a few razormaw hatchlings, well-oiled cloaks, blues or other assorted 'valuables' for summons' to Quel' Danas/Deepholme!
