General:
* Beggar
* Destitute
* Indigent
* Needy
* Poor
* Wretched
* Penurious
* Impecunious
* Down-and-out
More formal:
* Proletarian (emphasizes social class)
* Underprivileged (focuses on lack of resources)
* Deprived (emphasizes lack of basic necessities)
More poetic or figurative:
* Starveling (suggests extreme hunger)
* Tatterdemalion (emphasizes ragged clothing)
The best synonym will depend on the specific meaning and tone you want to convey.