Chalice of the Void and Lotus Bloom

[BreathWeapon]

Chalice of the Void at 0 counters will counter a 0cc spell, but Lotus Bloom has no cc printed on the card. I know that a Mind's Desire can reveal a Lotus Bloom and still cast it as a 0cc spell, but I haven't seen a ruling regarding Chalice of the Void and no cc spells.

[lordmayhem]

Chalice set at 0 will counter the Lotus Bloom.
The lack of a mana cost will prohibit you from playing it, however it does not change its converted mana cost, which is 0.

[Anusien]

Cards without a casting cost have a converted mana cost equal to zero.

You're not correct on the Mind's Desire interact.  Lotus Bloom's actual casting cost is {}, the empty set.  You can never pay "NULL" mana, so you can never pay the casting cost of Lotus Bloom.  It has a converted mana cost, so effects that check or make you pay the converted mana cost (Spell Blast) work.  The reason Mind's Desire interacts favorably with Lotus Bloom is because Mind's Desire lets you play the spells without paying the mana cost.  The only thing that stops you from playing Lotus Bloom normally is that you can't pay the mana cost.  Mind's Desire circumvents that.