I've had a blogspot blog that i started back in 2005, although never updated, until today - would it be a good start for serps?, and would it be beneficial for people to start commenting to it? the site is in my signature, any ideas for promotion is helpful. feel free to comment anything relevant to the subject including links
If the site has been indexed by Google since 2005 and you have had some backlinks for it since then, it might be useful. Otherwise, you shouldn't expect miracles.
If not promote the blogs will never get any benefit from it, update its with useful information and promote properly through forums , adds dir etc
You should get some back links to it because age of domain alone is not enough to get a good position on search engine. If you are serious with blogging then you should consider on getting your own domain.