It is a bit of a demand but does anyone have any suggestions for effective free advertisments? :o

Advertising what?
What you are looking to advertise would make a bit of a difference to what is effective for you ;)

Now that Gmail has evolved maybe we can all start spamming the accounts for beta testing the filters. LOL

That doesn't really help...
You will need to be a bit more specific.
To get effective advertising you have to advertise somewhere that has a target audience for what you want to advertise.