I just released a new service which is called "MyKeys". The idea behind this is
to have a summary of several account holdings.
All you need to do, is insert the public keys and create the summary.
No login or registration required: https://smartstellar.org/mykeys/
I also prepared two samples:
See all Stellar Exchange Holdings, accounts taken from stellar.expert: https://smartstellar.org/mykeys/publicnet/HUVD4ER
SDF Holding, accounts also taken from stellar.expert:
Click "Create", if you want to create your own list.