If your computer saavy enough you could create a website about how much you love her. You could make it private or public all depending on what she would think about it being public... An easy way to do this would be to create a "lovespace": You've heard of myspace, everyone has! If you don't have myspace page already you should. its really easy to start one up!

IM: Send her little cutsie IM's while at home or at work. Depending on if you can send IM's while at work. I don't want you to get in trouble if your company has something against this!

eMail: Send her a romantic or cute email.

Txt Messages: You can send her a txt message via the computer if you know which carrier she has. Just visit the carriers website and do a search for sending a txt online.  If you don't normally text her send her a quick message while she's away.  It will surprise her and put a smile on her face.  

Flowers: Send her some flowers just because...

Videos: With todays camera phones and digital cameras its very easy to make a video and post it online. Again you can make it public or keep it private. I used windows movie maker to make a valentines video for my sweetheart and she really loved it!