Since 1948, perhaps the single most unifying issue in the Arab world has been "the Palestine Question." The notoriously fractious Arab world would unite as one in passing Arab League and UN resolutions supporting the Palestinians and opposing Israel. Privately, many Palestinians scoffed at this show of support even as they publicly welcomed it. "Words and no action," they complained.
Actually, the nature of Arab support for Palestinians has varied widely over the last 60 years, and there has always been a wide gap between rhetoric and reality. In the 1930s and '40s it was built up by the tireless work of the Mufti of Jerusalem, Haj Amin el Husseini, who brought the Palestinian cause to the attention of Muslims as far as India. Partly thanks to him, the Arab states opposed the Partition Plan at the U.N. in 1947, vociferously if not cleverly. Partition passed, the Zionists prepared their government in waiting, and the Arabs did little. War was promised by the Arab states if the Jews dared to declare a state, though it is now clear that Arab generals warned their presidents and kings that their armies were woefully unprepared. The leaders were caught, however, in their own rhetoric, which led to the Arab debacle of 1948. Only the Arab (Jordanian) Legion fought well, and it is clear that they were fighting for specific territory and Jerusalem, and not seriously attempting to destroy the Jewish state. Palestinians pointed out cynically that each Arab state that sent troops hoped to profit from the war, and they were largely correct.
In the 1950s through the '60s, the Palestinian cause was largely quiescent. Neither the Sinai Campaign of 1956 nor the Six Day War of 1967 really involved Palestinians. Arab rhetoric volleyed and thundered; Arab leaders vied with each other in the harshness of their denunciations, even calling each other Zionist tools; but little was done. To be fair, most Arab countries extended some significant degree of openness and help to Palestinian refugees, but only Jordan gave them citizenship. Israel criticized the Arab states for not providing the haven Israel had provided to Jewish refugees from the Holocaust, which would, from an Israeli point of view, have provided the perfect settlement to the Palestinian problem.
Israel further accused the Arab states of using the Palestinian issue to distract Arab populations from their own shortcomings, and there is probably some truth to that. As noted, it presented an issue on which unity was easy, even if (or because) real action was impossible.
After 1967 and the Israeli conquest of the West Bank and Gaza, the Palestinians largely took their cause into their own hands. Jordan, which had still fondly hoped to regain Palestine, was reluctant to recognize the PLO as the "sole legitimate representative of the Palestinian people" but had no choice. The Yom Kippur War of 1973 had nothing to do with the Palestinians, nor did the ensuing Egyptian-Israeli peace process. Sadat tried to bargain with Begin on the issue, but Sadat's heart was in the Sinai and Begin's was in the West Bank, and each got what he craved. When Israel successfully removed the PLO in 1982 from Lebanon to Tunis, the Arab world did nothing.
The first intifada broke out in December 1987 partly because an Arab League meeting in Amman, for the first time, largely ignored the Palestinians. After the Gulf War the Palestinians had lost much of their Arab support, and thus were desperate enough to engage in the Oslo peace process in the early '90s.
The Arab states, which had provided little support for the Palestinians in war, provided just as little in peace. In the 1990s, with the exception of Jordan and to some degree Egypt, the Arab states stayed largely aloof from the peace process. Bill Clinton tried unsuccessfully to enlist them at Camp David, but failed, as did the peace process.
It was only in 2002 that Saudi Arabia, which by then had largely lost interest in the conflict except as a cause that exacerbated anti-Saudi Islamism, pushed an unprecedented peace initiative through the Arab League. Even Iraq under Saddam Hussein accepted it. It fell with a thud, not helped by the fact that it coincided with the worst suicide bombing in Israel, at a Passover seder, followed by Israel's "Defensive Shield" Operation in the West Bank.
At the beginning of Israel's 2006 Lebanon war, Saudi Arabia, Egypt and Jordan, in effect backed Israel against Hizbullah, thus demonstrating clearly that they are far more worried about Islamism than about Israel. The next year Saudi Arabia, taking an increasingly prominent role, had the Arab League re-pass its peace initiative. By now, radical leadership against Israel is led by Iran and the Islamists; the Arab states really do want peace, even if (and largely because) their populations are increasingly excited by Islamist rhetoric, which is both anti-Israel and against the existing regimes.
At this point, Israel could change the whole equation by accepting the Arab Peace Initiative as a basis for discussion, which is all that Fateh and the Arab states insist on. If they did, and negotiations succeeded, then a new axis could likely be formed between Israel, a renewed and empowered Palestinian Authority which would have to accept Israel to become a state, and most of the Arab states, against Iran and the Islamists. But this is the Middle East. It makes too much sense. Don't hold your breath.