(Original post by mariachi)
OK, since no one answers, I would say this :
few Muslims would gladly accept to be classified as "modern" or "modernists"
With regard to "classical" Islam : belly-dancing would fall under the general prohibition for women to exhibit their charms:
"And tell the believing women to lower their gaze and be modest, and to display of their adornment only that which is apparent, and to draw their veils over their bosoms, and not to reveal their adornment save to their own husbands or fathers or husbands' fathers, or their sons or their husbands' sons, or their brothers or their brothers' sons or sisters' sons, or their women, or their slaves, or male attendants who lack vigour, or children who know naught of women's nakedness. And let them not stamp their feet so as to reveal what they hide of their adornment. And turn unto Allah together, O believers, in order that ye may succeed."
Therefore, belly-dancing should be considered as haram, except if the public is composed exclusively by females. Only males acceptable would be mahrams (the close relatives listed above) , children and eunuchs.
In any case, accompanying music should be non-instrumental : this is based on a famous sahih (authentic) hadith by Bukhari
Volume 7, Book 69, Number 494v:
Narrated Abu 'Amir or Abu Malik Al-Ash'ari:
that he heard the Prophet saying, "From among my followers there will be some people who will consider illegal sexual intercourse, the wearing of silk, the drinking of alcoholic drinks and the use of musical instruments, as lawful. And there will be some people who will stay near the side of a mountain and in the evening their shepherd will come to them with their sheep and ask them for something, but they will say to him, 'Return to us tomorrow.' Allah will destroy them during the night and will let the mountain fall on them, and He will transform the rest of them into monkeys and pigs and they will remain so till the Day of Resurrection."
There seems to be an exception for one-membrane drums (duff), but only during wedding celebrations.
"It is reported regarding Hazrath Umar (R.A.) that if he heard the sound of a duff he would immediately send somebody to investigate. If it was found to be the occasion of a Walima, he would not do anything. Otherwise he would go for his whip (i.e. he would forcefully stop the playing of the duff) (Fathul Qadeer - Vol. 6, Pg. 389)" http://www.beautifulislam.net/halalharam/music.htm
Hope this helps