A couple bloggers, including Lord Kilgore, have been discussing the weakness of 1st level magic-users and how to beef them up (with the B/X Blackrazor blog posting the contrary view.) I'm kind of leery of the magic blast solution because it seems too flashy and seems a bit overpowered, but I think it's basically fine for those campaigns where it fits.
If you look at the problem in comparison to fighters, or to non-beefed-up magic-users throwing daggers, in a world where all weapons do 1d6 damage, there's not much difference between a fighter swinging a sword repeatedly, a non-beefy 1st level magic-user throwing multiple daggers, or a beefy magic-user zapping enemies with a d6 bolt. They are all mechanically identical and mostly balanced. The "too flashy" objection is because in my personal conception, magic is mostly mysterious and unseen, rather than visible rays of light; that's easily fixed, of course. The "overpowered" objection is because the magic blast, unlike either a thrown dagger or a spell, is reusable at will, which makes it distinct from missile and thrown weapons in general; furthermore, it can't be stolen, like a real weapon. The solution here is to make "extra" low-level magics more like equipment.
One solution, based on Holmes Basic, is to allow 1st-level magic-users to create scrolls. Holmes gives a base cost of 100 gp/spell level. I've mentioned this before, but here's a new idea: cantrip scrolls cost less, maybe a fifth less: 3d6+2 gp for common ingredients, and you can use ordinary feathers and sap/blood for the ink base, instead of magical or extraordinary sources.
Here's a related idea: cantrip wands/staves. These let a magic-user cast a specific cantrip repeatedly, with a risk of breaking from the magical forces directed through the wand. The magic user has to know the cantrip, but doesn't have to prepare (memorize) it. It costs 100 gp to place a single cantrip in a wand or staff; higher-level magic-users can add additional cantrips (one per HD, 100 gp cost for each,) but there is a risk of the wand or staff bursting into flames during the process, destroying it. This is a little more like "equipment" than the innate at-will magic blast ability.
Here's a new cantrip to make this useful in combat:
Bolt of Bedevilment
Fires an invisible dart at an opponent, which takes 1 point of damage; roll a d6 for "full" damage, however, and compare the tripled result to either Strength, Dexterity, or other attribute, depending on the aime of the bolt; if the die roll is higher, the opponent drops a weapon, trips, or is distracted.
Edit: Oops, forgot to add that the Bolt of Bedevilment is blocked by any sort of enchanted armor.
Edit 2: Per Lord Kilgore's comment below and my response, the cost of a cantrip wand or staff might be lowered to the cost of a cantrip scroll plus 10 gp, plus the cost of the wood itself, unless MUs look for a branch or limb and prepare it themselves.