Terran players love their siege tanks about as much as they love their wall ins and a line of siege tanks backed up by marines can be tough to crack. I recently found out about a neat trick that will harass and soften up the siege tanks while keeping your forces (mostly) out of harms way.
The key to the strat is that when sieged up the tanks deal area of effect damage to everything, including friendlies, around their target; that's how they chew holes in your blobs so quickly. To exploit this AoE get a few infestors and research burrow. Burrow them and have them drop some infested terrans, one at a time, into the siege tanks like so:
The tanks will turn around and fire on the egg, damaging friendlies! Keep this up and you can severely soften up or even destroy the Terran forces. It is also quite annoying for the player to deal with.
One thing to note here, send in one infestor at a time or at least keep them spread out. That way the player cannot catch more than one infestor with a scan which will reduce your losses. Do as I say not as I do.