I've been using this account for a while, but my OpenID provider lately has been giving some strange errors and other issues. It seems I've ended up creating another account with the same name on the main stackoverflow site, associated with my Google account instead of my Blogspot account (even though Blogspot is part of Google?). Can these be merged?
Yes, they can indeed merge your accounts.
Flag one of your own posts for moderator attention and explain the situation.
As soon as a
comes along, they will verify that both of the accounts indeed belong to you and then your accounts will be merged.
You might want to ensure that you list the same email address on both account profiles as this is a good indication for a moderator that the accounts are related.
If all else fails you could always send an email to the SO team requesting an account merge - firstname.lastname@example.org