I have been to a close friends blessing way and it was beautiful. I am not sure just how spiritual or out there you want your experience to be, but here are a few things that we did at hers.

We each brought a bead for the birthing/breastfeeding necklace and had a circle where we all held hands and had a moment silence where we put our positive energy into the beads. Then as we were threading the beads on the necklace we each said a few words to the expectant mother and gave her our blessing.

Each of us brought a candle as well and then from the master candle the expectant mother had, we lit each of our candles. When we found out she was in labour we each lit the candle and thought about her at that moment (obviously only if we were home or able to),also she now is onto her second candle that was lit from the first candle and will burn forever from the same flame.

Also, We all added to a photo album a photo and a blessing. Can be used to get support and strength from in the final days of her labour and during labour. you can keep it as a keepsake for the baby.

We also had moment where we acknowledged that this was her second child as her first was a miscarriage at 10 weeks and had a moment where we spoke about that. Though it depends on how you feel.

I know it may be a bit out there but that was my experience of one. I also helped her out organizing it and looked on the net for some ideas. There are many out there!
I hope that helped a bit.