What to do with many L1 resonators?

If you don't need them, give it to your faction L1 players, so that they can deploy them and therefore level up.

L1 resonators are perfect to booby trap the portal, as it will get destroyed very fast especially if put close to the strongest resonator, the owner of the resonator will get notified once it is destroyed and can counter attack - recharge the portal remotely.

Just recycle them. They are so useless and easy to get that you could better use the XM gotten by recycling them than bothering on dropping them so your friends could pick them up. They will be in your same situation of too many of those.

The other alternative is always deploy them first then upgrade them. If you have the time at an unclaimed portal you could deploy 8 L1 and the start upgrading to L2 and keep going up to your max of 1 L8, 1 L7, 2 L6, 2 L5, and 2 L4.

If you do this correctly you could deploy up to 45 resonators on a single portal instead of just 8 and get faster your Builder medal.
_{1 1 1 1 1 1 1 1
2 2 2 2 1 1 1 1
3 3 3 3 2 2 2 2
4 4 4 4 3 3 3 3
5 5 4 4 4 4 3 3
6 6 5 5 4 4 4 4
7 6 6 5 5 4 4 4
8 7 6 6 5 5 4 4}