I like nothing more than a birthday card. Celebrating my birthday at whatever time of year makes me happy, especially when I'm getting such a nice gift
That being said, a thank you note and generous show of appreciation for something nice I forgot I did, or a congratulatory gift and card for some accomplishment... I'll celebrate Christmas at whatever time of year, too
... it turns me on.
Sometimes I'm not sure if the guy is expecting me to open and read the card right away, like I would if it were really my birthday (especially if he is a total newbie)? Atleast I glimpse at it in the bathroom and note the generous gift.
Not a big fan of the white envelop nor the bank envelop, but I understand that getting me a birthday card isn't always convenient- it's the thought behind the cash gift that counts.