How to deal with an abandoned home
Call the owner
If the town's not going to do anything immediately, you can search property tax records to find out the name of the owner.
You can find this with your county government (many of which have put their databases online). These records may have another address for the owner, which could lead you to a phone number as long as they're listed.
If it's a tenant who has left, a landlord might not know, especially if the tenant was already deadbeat or a family member who was supposed to be maintaining the property in exchange for a free place to live.
If the owner isn't particularly interested in changing the way he or she treats the property, you can at least get permission to cut the lawn or clear the sidewalk. That way, you can't be arrested for trespassing.
Make sure you write down when you talked to the homeowner, and notes from the conversation, just in case.