"So light a fire!"
"Yes -- of course -- but there's no wood!"
"HAVE YOU GONE MAD?... ARE YOU A WITCH OR NOT?"
-- Harry, Hermione, and Ron (PS16)
Creates a quantity of blue flame which can be directed to a specific place or kept in a jar.
References from the canon
Hermione cast a bluebell flame that could be carried around in a jam jar, sent out a short distance, then retrieved into the jar; she used it to set Snape's robes on fire during the first Quidditch match of her first year (PS11). She used this spell against Devil's Snare when working through the challenges surrounding the Philosopher's Stone (PS16).
Portable, waterproof fires are a speciality of Hermione's (CS11).
"bluebell" - a flower with blue blossoms
Bluebell flames are similar in nature to Professor Lupin's "hand held flames" in the train car when Dementors stopped the Hogwarts Express (PA5). However, his fire was not blue like bluebell flames, so we can't be sure what spell he used.
The fire in the Goblet of Fire may be this or something similar; it is described as blue and it sits in a wooden goblet without burning it (GF16). -BB