I created a photo library in SharePoint 2010 with LOTS of photos going into it. I use windows explorer view to drag photos from the server to the library. The photos all show checked out to me, and I want to check them in (and possibly disable the check-out/check-in feature altogether.
There are a couple of things to check to ensure documents are not automatically checked out:
1) Go to the Library Settings and ensure there aren't any required fields
2) Go to the Library Settings > Versioning Settings. Ensure content approval required is turned off and require check out is turned off.
To check-in the ones you already have checked-out, you will need to select them all in the web browser and click check-in on the ribbon. Alternatively, you can use SharePoint Designer to connect to the site and check-in the items (this may be easier for you doing it in bulk).
Also note that you should be able to select the items in the view and use the "Check in" option from the ribbon. Be sure to use a normal list type of view to do this. Perhaps you can create a view that filters items that are checked out to you filtered on your username and go from there.