Steam Vents (x2) lets you get both colors untapped, and it's fetchable, but at the price of 2 damage. Damage adds up with lands and Gitaxian Probe, so be careful as Shivan Reef can be a pain late game.
Flooded Strand (x4) thins the deck so you don't draw lands, and fetches Steam Vents, or if you're low on life, a basic Island. Scalding Tarn is less budget and strictly better in that it finds a basic Mountain which I would recommend 1 of if you're running a playset of tarn, and otherwise none. Shuffling the deck can be bad once you know the bottom or top of your deck from Serum Visions or Sleight of Hand, and shuffling can be good or bad with Peer Through Depths, depending if you missed a land, Pyromancer Ascension, or Goblin Electromancer that you would want shuffled back in.
Polluted Delta (x2) is nice for the same reasons as Scalding Tarn, but you can't fetch a basic Mountain. However, is more vital than because your draw spells cost and your rituals produce . Flooded Strand (x1) also works. Again, pros and cons of shuffling. Split the non-Scalding Tarn fetches as evenly as possible for optimal play (against Surgical Extraction effects)
Spirebluff Canal (x4) gets you either color untapped turns 1-3 (assuming you hit your lands drops). Turn 3-4 win is the goal, so while drawing into one in dire need of untapped mana turn 4 is bad, you can probably dig out an untapped land with all the draw you've got on turn 4. I say it's worth running 2, because life total really can mean the difference of having an extra turn to storm off, especially with aggro meta, painful lands, and phyrexian mana Gitaxian Probe. Finkel (God of storm) says here that he's adding 4 Canals and cutting 1 Vents, 1 Fetch, and 2 Reefs. However, I think running the full playset might be rough if you're trying to find untapped mana turn 4, but life is increasingly important now, so I think 3 is the number.
Shivan Reef (x2) gets you either color untapped, but assuming a turn 3 or 4 win, you'll pay 1-4 life depending when you drop it and if you ever tap for colorless (perhaps Past in Flames). However, you'll rarely tap for . Assuming no tap for and a turn 4 win, and equal likelihood of dropping it any of those 4 turns, you're taking an average of 2.5 life, so compare to 0 for a basic, 1 to fetch a basic, 2 to shock, 3 to fetch a shock.
Island (x2) is fetchable in order to get untapped without paying 2 life. Generally preferred to Mountain because draw spells are and rituals produce .
*Budget sidenote: I generally don't talk much about budget, but if you're running Scalding Tarns instead of cheaper fetches, then add a Mountain (duh, but just thought I'd mention it). Also, you can totally run 1-2 more Island, Shivan Reef, and/or Sulfur Falls (but if you run falls, I'd cut reef and/or spirebluff) for budget reasons, but if you're running fetches, 2 Steam Vents are crucial.