General:
* Extravagant
* Profligate
* Prodigal
* Unthrifty
* Inefficient
* Uneconomical
* Squandering
* Dissipated
* Luxurious (when referring to excessive spending)
More specific:
* For resources: Consumptive, spendthrift, improvident
* For time: Dilatory, time-consuming, inefficient
* For money: Frugal, penny-pinching (opposite)
The best synonym will depend on the specific context in which you are using the word.