Four from Compiler Science:

1. Does a program ever access an uninitialized variable.
2. Do two context free grammars describe the same langauge.
3. Does it make a difference if parameters to a subroutine are passed by reference or by copy-result
4. Deadlock determination in parallel programs.

Actually almost every question of the form "Does a program ever do X?" is equivalent to the halting probelm. So the above might be considered too close the the halting problem to be interesting answers ot this question.

Four from Compiler Science:

1. Does a program ever access an uninitialized variable.
2. Do two context free grammars describe the same language.
3. Does it make a difference if parameters to a subroutine are passed by reference or by copy-result
4. Deadlock determination in parallel programs.

Actually almost every question of the form "Does a program ever do X?" is equivalent to the halting problem. So the above might be considered too close the the halting problem to be interesting answers ot this question.