In D&D 3.5, is there any method of casting spells that fit in the lvl 0 spell slot without being limited to a number of times/day? The goal is to cast Prestigitation an unlimited amount of times/day due to the usefulness of turning people's hair hot pink. I am willing to take feats for this.
My character is at level 12 with 5 levels in factotum and 7 in chameleon.
Also, I believe I found a hint which is in some Therafirm Setting: http://therafim.wikidot.com/versatile-spellcaster
Which says: "Special: In Therafim once you gain Unlimited Cantrips you may still only sacrifice up to your normal daily allotment of cantrips to fuel this feat."
Best Answer
The best method (as long as you can get your DM to agree) is probably a custom magic item.
From Complete Arcane (page 80), the feat Innate Spell allows you to cast one spell of your choice as many times/day as you like. However, it requires you to have the Quicken Spell, Silent Spell, and Still Spell feats, as well as permanently losing one of your 8th-level spell slots.
The D'hin race, from Dragon Magazine 350, page 56, get at-will prestidigitation - only a +1 level adjustment, which you may find easier to swallow.
While it won't let you cast prestidigitation an unlimited number of times per day, the metamagic feat Persistent Spell could be used to make a single casting of prestidigitation last 24 hours, allowing you to use its various effects all day. Unfortunately, this will require it to be cast from a 6th-level spell slot, so you'll have to look into ways of reducing metamagic costs (there are too many to list here, although Arcane Thesis is probably the simplest).
In the same vein as Persistent Spell, with your DM's permission, permanency could be used to give you a permanent prestidigitation, allowing you to use its effects whenever you want.