None of the employees where invited, but we get a long pretty good, we around the same age and ever since he proposed he always tells me things about the whole wedding planning and the new house, how exciting everything is, and I like that because I'm basically a newly wed too so I love seeing people getting married.. any way.. I feel like I need to give him a little something! Any suggestions?

In my office, we chip in on these things and keep the individual contributions inexpensive, and the gifts useful and nice but not too personal. When a supervisor in my office got married, we each put in $20 and got him a nice card with a gift certificate to a nice restaurant for a date night.

If nobody is invited to the wedding, and there is no contribution going on to get a card or gift certificate (which is a nice idea), then I'd say at most, a card is appropriate.

I agree with both members above.
Another idea is to host a pot-luck at work to celebrate. Even those who don't like to give money toward a gift, like to eat ;)

That is a really great idea!