The set $M=\{1,2,\ldots,2007\}$ has the following property: If $n$ is an element of $M$, then all terms in the arithmetic progression with its first term $n$ and common difference $n+1$, are in $M$. Does there exist an integer $m$ such that all integers greater than $m$ are elements of $M$?
1. We start by analyzing the given set \( M = \{1, 2, \ldots, 2007\} \) and the properties it satisfies:
   - Property (a): \( 1, 2, \ldots, 2007 \in M \).
   - Property (b): If \( n \in M \), then all terms in the arithmetic progression with the first term \( n \) and common difference \( n+1 \) are in \( M \).

2. Let's consider the arithmetic progression starting with \( n \) and common difference \( n+1 \). The general term of this progression is given by:
   \[
   a_k = n + k(n+1) = n + kn + k = n(1+k) + k
   \]
   where \( k \) is a non-negative integer.

3. We need to check if there exists an integer \( m \) such that all integers greater than \( m \) are elements of \( M \). To do this, we need to see if the arithmetic progressions can cover all integers beyond a certain point.

4. Consider the smallest element in \( M \), which is \( 1 \). The arithmetic progression starting from \( 1 \) with common difference \( 2 \) is:
   \[
   1, 3, 5, 7, \ldots
   \]
   This sequence includes all odd numbers.

5. Next, consider the element \( 2 \) in \( M \). The arithmetic progression starting from \( 2 \) with common difference \( 3 \) is:
   \[
   2, 5, 8, 11, \ldots
   \]
   This sequence includes all numbers of the form \( 2 + 3k \).

6. Now, consider the element \( 3 \) in \( M \). The arithmetic progression starting from \( 3 \) with common difference \( 4 \) is:
   \[
   3, 7, 11, 15, \ldots
   \]
   This sequence includes all numbers of the form \( 3 + 4k \).

7. We continue this process for all elements up to \( 2007 \). Each element \( n \) in \( M \) generates an arithmetic progression that includes numbers of the form \( n + k(n+1) \).

8. Since \( M \) includes all integers from \( 1 \) to \( 2007 \), and each integer \( n \) generates an arithmetic progression that covers infinitely many integers, we need to determine if these progressions collectively cover all integers beyond a certain point.

9. Notice that for any integer \( n \) in \( M \), the arithmetic progression \( n, n + (n+1), n + 2(n+1), \ldots \) will eventually cover all integers greater than \( 2007 \) because the common difference \( n+1 \) ensures that the sequence grows without bound.

10. Therefore, there exists an integer \( m \) such that all integers greater than \( m \) are elements of \( M \). Specifically, \( m \) can be chosen as \( 2007 \) because the arithmetic progressions starting from each \( n \in M \) will cover all integers beyond \( 2007 \).

The final answer is \( \boxed{ m = 2007 } \).