I been listening to podiobooks for a while now. Mostly science fiction and fantasy.
I would recommend:

Shadowmagic (Very good)
Billibud Baddings and the Case of the Singing Sword (Very good)
The Pocket and the Pendant (Very good and child safe)
Nina Kimberly The Merciless
The Flown Sky (Children Orientated)
Under the Stairs (Good story if you don't mind the narration style)

<Edit>Just finished "Singularity". Very good sci-fi novel. </edit>

The hard part with Librivox if finding what you want. The Sherlock Holmes books are there although the narration quality varies.