Which low-skill labors only reduce time

My fortress is starting to grow, just under the 80 mark with my last migration wave. And, well, I'm getting a lot of unskilled dwarfs migrating in that I'm simply designating as "peasants" to do all the menial jobs.

Essentially, I really only want to assign labors to these guys where by the only thing that changes at higher levels is the speed of the job. I don't mind having lots of slow peasants, but I don't want peasants wasting my metal making low quality goods, if you see what I mean.

Many of the pages on the wiki seem to say what the skill affects, but I wonder if there's an overview somewhere as there's a lot of labors to trawl over...

Or maybe, what labor set do you guys allocate to your "peasants"?

Some labors may or may not fall into this category, depending on what actual tasks you tend to run in your workshops, and your personal play style.

EDIT: separated "only affects speed" labors from "affects quality but you probably won't care" labors.

Labors that only affect speed

• All hauling tasks. This is what peasants excel at. Nothing beats designating 'dump' on that 30x30 strip mine and watching your peons clear it in a matter of moments. Or furnishing those twenty rooms before the migrants can even get from the edge of the map to the fortress doors.
• Wood cutting can be useful, but you may want to have some spare axes so your peasants don't steal them all and not leave any for your axedwarves. (As a bonus, your armed peasants will stand a slightly better chance if they do end up in a fight.)
• Stone detailing, if you're willing to micromanage a little. Skill is unimportant for smoothing, so you can designate large areas to smooth and send your peasants to it. If you designate engraving, however, you'll want to disable this labor again on your peasants so you don't get ugly carvings everywhere.
• Feed patients/prisoners and recovering wounded
• Wood burning, furnace operation and other "tier 2" ingredient production tasks. Many of these production tasks have set formulae (e.g. 1 bituminous coal + 1 fuel = 3 fuel). Skill has no effect on production except for the time it takes. If you hit a couple good coal veins, it could be very useful to have a bunch of smelters set to make coal into fuel, or ores into bars, set to repeat.
• Plant gathering, if you feel the need, although farming is generally preferable.
• Farming (Planting). Usually one full-sized farm plot and a couple skilled planters are enough to keep a fortress going, especially if you buy any food or drink from caravans. However, it might work well to have lots of peasants with planting enabled, rather than a couple dedicated farmers, but I haven't tried it.
• Cleaning. Very useful when you wipe out a dozen ambushers at the gate and everyone is tracking blood all over the place.
• Pump Operating, although dwarf-powered pumps are generally of limited use.

Labors that affect quality (but you probably won't care)

• Architecture. Skill does not affect building speed. It does have an effect on the quality of constructed buildings, but this is generally very minimal (as outlined in the linked article).
• Mechanics, in some cases. The quality of mechanisms, traps, etc. is not terribly important, unless you really want Urist McLookyLoo to be ecstatic about that Fine Stonefall Trap he saw last week. EDIT: Mechanism quality does affect trap quality, as pointed out by Raven in comments.

Armed with sjohnston's list, you can gain some level of control over who does the skilled labors by designating a Manager (nobles screen) and utilizing workshop profiles.

With a workshop's profile you can permit or forbid individual dwarves from using the workshop, and/or set minimum and maximum skill levels for the use of that workshop. In this way, you could have one set of workshops for your novice-masons dedicated to the creation of rock blocks (blocks' value are not increased by the mason's skill) and another set of workshops for your master-masons dedicated to the creation of stone furniture (for example). This saves you from juggling labors for certain things.

Unfortunately, this approach is not entirely compatible with using the jobs manager screen (j,m) to designate tasks, as your manager doesn't know which workshop should get low-skill or high-skill jobs. In the above example, you'd just have to order rock furniture and rock block production at the workshops themselves.