Mr Postman always seems to work with me and thunderbird with my hotmail accounts.
I haven't got round to sorting out Gmail yet as I normally check that in work anyway.
Seeing Microsoft are going to block Outlook Express using hotmail from next year anyway they'll probably block most of the third party add-ons at that time as well, so you might be stuck to checking it in Firefox anyway.
http://www.theinquirer.net/?article=18718