Many forumers have mentioned some symbols and customs in Islam. Lou also made a very important points with regards to the five pillars of Islam (although it is in this order, only sawm and zakat are mixed up
): Shahadah, salat (prayer), sawm (fasting), zakat and hajj.
The Kab'ah is an important symbol itself as it is the direction to which we pray to - i.e. all Muslims pray towards the Kab'ah The Hijab is another as well as the type of skull caps which the men wear, especially during prayer. It is similar to the Jewish skull caps except it is more bigger. Something like this:
And usually brown, black or white is worn. It's not a major symbol but many of the faithful men wear it.
The crescent moon is much very a symbol in Islam as you see them on the top of the minarets of the mosque. Don't think the star is that much of a significance though.
The 'tasbeeh', which is similar to the rosemary beads, is also an important symbol in Islam. It is usually used/said after each prayer although some people carry it around just for continuous remembrence of Allah (SWT).
It is divided into three parts. If you look at the image, there's this little tower like thing which divides it into three parts. Each bead is equal to the amount of 'Subhan'Allah's, 'Alhumdulillah's' and 'Allah'Akbar' that is to be recited.
I think that's basically it