In the Roman rite, the Easter Vigil service of Holy Saturday night starts with the blessing of fire and the lighting of the Paschal candle. The Orthodox churches have a similar rite in the Divine Liturgy said on Great and Holy Saturday, called the “Blessing of the New Light”: “Shine, shine, O new Jerusalem, for the glory of the Lord has shone upon you.”
In Jerusalem’s Church of the Holy Sepulcher (a/k/a the Church of the Resurrection), the arrival of the New Light is taken as an annual miracle in which fire descends from Heaven to the candle of the Orthodox patriarch who prays for it in the tomb of Christ; and from there it is given to the faithful in a rush of candle-lighting. The miracle, so it is said, happens in various forms.
The Telegraph says that tensions between the various churches sharing the basilica were a bit high this year, understandably enough:

Relations between the clergy who preside over the miracle have been inflamed since last year when the ceremony was marred by a brawl within the shrine.
Out of sight of the faithful, the two churchmen – the Armenian participating for the third time, the Greek for the first – fiercely disagreed on a matter of precedence. Should the Greek patriarch emerge first with the Holy Fire or the Armenian? Would the Greek or the Armenian Orthodox community be first to receive the light?
When Patriarch Irineos fought his corner by twice blowing out the Armenian’s candle, the Armenian felt obliged to resort to a shameful expedient to obtain some Holy Fire.
“In this worst situation I had to use my emergency light, a cigarette lighter,” he later admitted.

Happily, Voice of Russia radio mentioned in its news today that the bishops worked out a last-minute compromise to conduct the rite, and when they did so, the candles of the faithful spontaneously and simultaneously took fire. So they say.
As the Telegraph writer mentions, Catholics do not participate in this rite, even in years when our Holy Saturday falls on the same day as that of the Orthodox; and I don’t think Catholics are obliged to believe any related claims of miraculous goings-on. In fact, an inside participant has given his description of what really happens at the tomb.
(But if you are looking for a visible miracle to celebrate, let’s just rejoice in the fact that the old Soviet Communist station Radio Moscow has been sufficiently converted that it reports this Christian event favorably.)