I think the cake sounds like a good idea; food is always good.
For figuring out what to get someone, think about their hobbies, clothes they like, anything they've commented on in the past that they think is neat/would like to have, things that would be fun to do (I'm thinking of tickets to stuff), etc.
What kind of things have you gotten your significant others in the past?
Kirk's birthday was actually the day before I met him. He likes hoodies as much as I do and loves his school, I got him a very nice Valpo hoodie (Valpo is the university he went to). I'm not sure if he had one (if he did it may have been old and kind of worn out). Anyway, that gift was well recieved, as he wears it all the time (even in the summer because he is cold natured like me)
Then for Christmas last year, I got him a few different things -- new work shirts, a Hawkeyes shirt, some wireless headphones for webcam chatting/gaming, and uh... probably something else I can't remember anymore. Those gifts I would rate as "meh" because it was early in the relationship and I got the shirt sizes wrong. And the headphones broke
So, fail.
For Valentine's day, I made him a photobook with 26 reasons why I love him to make up for "all the Valentine's days I missed" (he had never had a girlfriend on Valentine's day before). This went over quite well because in the months before V-day he had been telling me all kinds of reasons why he loved me and one night he was like, "hey, you haven't told me any reasons why you love ME". I think I was already in the process of making the book whenever he had said that (much to my delight), so I told him I'm not as "good with things like that on the spot" and I'd have to "write some down". Then he brought it up again like a week before V-day (which was amusing because at this point he seemed a bit concerned about it) and suggested maybe I write some in a card. I was having a good time with this
I asked him how many reasons he thought I could come up with and he was like I don't know... 5? 12? Then of course on V-day he got the book with 26.
(Just FTR I normally would have gone much, much less sappy for V-day. Probably made a nice dinner or something. But, we're long distance so that wasn't possible.)
Then for his birthday this year, my parents and I split the cost on a GPS from all of us. Kirk has nicknamed it his "other girlfriend".