General Synonyms:
* Ooze
* Trickle
* Percolate
* Leak
* Dribble
* Exude
* Filter
* Strain
More specific synonyms:
* 滲透 (shèn tòu) (Chinese, meaning "permeate") for describing liquids moving through a porous material
* Percolate (for liquids moving through coffee grounds or other filters)
* Emanate (for a subtle, slow release of something, like gas or odor)
The best synonym will depend on the specific situation and the type of substance seeping.