Visiting 108 Siva temples in one's lifetime is said to absolve one of all sins and attain bliss. Is there a specific list of 108 temples or does it refer to any 108 out of the thousands of Siva temples?
Glad to know about your ambition.
To best of my knowledge there are saints in vaishnava philosophy called Azhwars who sung songs in Tamil in which the name of the temple or its place will be mentioned directly or indirectly.
While these Azhwars composed these songs no such coherent list of 108 temples exist (here I mean no such list exist and I am not saying that no such temples exist). The songs that are referred here are 4000 divya prabandhams. Later someone made up this list and as of now we follow that list even though there are some doubts and disputes where the temple cannot be exactly mapped to the current location.
So is the case for Shiva temples, which is called in Tamil as 'பாடல் பெற்ற சதலம்' (paadal pettra stalam) which means the temples that were sung. The songs that are referred here are devaram (that's all I know).
The list of such temples can be found in a map marked by a temple lover named Raju. If you can read Tamil, the list of such temples are provided in Tamil Wikipedia. In case if you can't there is an English site as well, but I am not sure how complete/accurate that is.
Other than this, I have a friend who has a Tamil book which lists all these and provides explanation, route info etc. If you want, drop a line in comment and I will try to get the details of that book.
Update: I stumbled on an archieve that lists the temples and its details similar to that book mentioned above.