We don't actually think there was much raiding of Muslim lands, although there are a few exceptions: (1) vikings based in southeast France raided Iberia—including the Muslim areas in what is now southern Spain—in 844, (2) western vikings again raided Iberia and passed through the Straits of Gibraltar to raid North Africa and southern France in 859-62 (for both these southern expeditions, see Ann Christys's book or a short paper on the same), (3) expeditions by the Rus against Byzantine targets might have passed through Islamic areas in 860, 907, and again in 941, and (4) runestones around modern Stockholm indicate an ill-fated expedition under a leader named Ingvar to the Caspian Sea, including Islamic areas, between 1036 and 1041.

In general, however, relationships between Norse-speakers and Muslims seem to have been built upon trade. We have a substantive number of Arabic references, which are enjoying a period of renewed attention thanks to a recent anthology and especially the scholarship of Thorir Jonsson Hraundal. We also have a large number of surviving trade goods that were produced in Islamic areas, particularly glass beads and silver coins. These coins were stamped with the shahada, which is the basic Muslim statement of faith: "There is no god but God. Muhammad is the messenger of God." These coins and their Arabic script were copied onto diverse materials, including pendants and possibly textiles. The textile evidence has recently been the subject of much debate, but for what it's worth, I think there's ample reason to believe that whoever embroidered them wanted to emulate or at least invoke Arabic script, even if there's merit to some of the complaints regarding how these textiles were first presented to the public.

So Scandinavian-Islamic contact was plentiful during the Viking Age and appears to have been, in large measure, friendly. But was there cultural transfer? That's a bit harder question to answer.

Although Viking-Age women wore glass beads made in the Abbasid caliphate, these seem to have been produced primarily for export and I know of no evidence that Islamic women would have worn similar necklaces. And although Viking-Age traders imported large numbers of silver dirhams, they tended to hack them into bits and trade them by weight rather than as individual coins. Gradually, however, Scandinavians adopted a coin economy by the end of the Viking Age, but by that point, they were more likely to be trading for West European coins than Arabic dirhams.

Nevertheless, I think the constant Scandinavian demand for glass and later silver were fostered primarily through contacts with the Islamic world. Western Europeans largely abandoned wearing necklace beads by 700, but vikings and Norse settlers carried them back into Western Europe and eventually all the way across the North Atlantic. And whereas during the preceding Iron Age, Scandinavians had evidenced a desire for gold, during the Viking Age, this gold demand disappeared as Scandinavians forged connections with the major silver-producing areas of the Abbasid caliphate, and in particular with the Saminid emirate centered in modern-day Iran.

In short, I don't think Islamic culture itself wended its way into Scandinavia during the Viking Age. But I think the evidence is clear that without the economic boom of the Abbasid caliphate, which fed the northern trade routes with glass and silver, Scandinavia would have looked much different during the Viking Age, perhaps enduring only as a backwater of the Carolingian world rather than as a locus of interregional change. So Islamic culture had an impact on Scandinavia and may have even been a driving force behind the Viking Age, but there's little evidence to support the argument that Islamic culture was itself imported.