I think that the roots of most major religions (especially Judaism, Christianity, and Islam) are very similar and that many texts and beleifs are based of of the same events/experiences as interpreted by different people. As far as doctrines go, they branch in separate directions, but the basic message of almost all religions is to the betterment of one's self and those around them by way of scriptural and moral code.

The difference and similarities between religions today is not in the religions themselves, but in how strictly they are interpreted. There is the strict interpretation, non-orthodox, and the other end which is much more liberal or modern. Sometimes people of different religions beleiving in a less strict interpretation of texts can have more in common than they can with the more conservative side of their own religion. This is especially true with Islam and Judaism in my opinion.

Religion at its roots is commonly a check against the worse natures of mankind in cultures, and many traditions and beleifs were created in religious texts to survive as a guideline for what was at one point the ideal or bettered society by some veiwpoint. Most of these beleifs are general truths about the good and bad sides of humanity. I guess thats kindof from a non-religious perspecitve though.

__________________
"...Follow the crystal star to the pyre of the flame; there exists the dwelling of the spreading fire. The heart of this life rests upon the fate of that place, and what begins there sends a contagion to the rest of the universe.
As long as the fire burns we shall never be free..." (The Shadows of Yavara, Final Reclamation)