Common words:
* Hello
* Yellow
* Follow
* Hollow
* Pillow
* Swollen
* Pillage
* Wallow
* Tallow
Less common words:
* Bellow (to roar)
* Jowls (fleshy parts of the cheeks)
* Knell (the sound of a bell, especially for a death)
* Quill (a pen made from a bird's feather)
* Swell (to increase in size or volume)
* Tell (to relate or narrate)
* Well (a deep hole for water)
Note: There are many more words with a double "ll", but some are more than two syllables.