I just recently repaired a hole in the nose of my friend's board, and it turned out really well. So well I decided I would do the same on my board and document it w/ pics, so hopefully it will help somebody in the future. Unfortunately it didn't quite go as smoothly as the first time, but the process is documented nonetheless and should still be helpful.
Disclaimer: Everything I know about working w/ fiberglass and epoxy I learned from reading the internet and working with it. I'm far from an expert and if you see anything I'm doing wrong please let me know so I can correct it.
So, here we go. Here's the hole in my board, I'm sure a lot of you have gotten this to varying degrees. Mine was repaired with some cheap 5 min epoxy a few years back and it had broken up and yellowed, so I took a butterknife and scooped it out.
For this job, I used MAS epoxies. I've used them before to make skateboards and I have no complaints. I got these at Boater's World. Notice I got non-blushing hardener, so it would dry clear and not yellowish. The stuff on the right is silica powder, it's really fine and when added to resin it hardens it up. It not only adds structural integrity, it also makes it thicker and easier to work with. Makes it less like honey and more like that little can of glue you used back in Kindergarten with the brush attached to the cap. The more you add, the thicker it gets, so just experiment.
I also picked up a little bit of fiberglass cloth, some rubber gloves, and some little paper dixie cups. When resin cures it gets surprisingly hot, and will melt a hole in a Styrofoam cup, so use paper. Not pictured is the dust mask (or better yet, gas mask) I should have been wearing.
MAS epoxy is 2 parts resin, 1 part hardener, so what I did was picked an arbitrary amount of water and filled the cup, then marked the line, and did so 3 times. I picked 2 tsp, but I could have gone less for this first batch. I could have used 1tsp.