General:
* Stingy
* Cheap
* Parsimonious
* Thrifty (can have a positive connotation, so be careful)
* Close-fisted
* Penny-pinching
* Tight-fisted
More negative connotations:
* Greedy
* Avaricious
* Scrooge-like
* Ungenerous
* Uncharitable
More formal:
* Frugal
* Economical
The best synonym will depend on the context of your writing.