We're planning on putting general (not specific) drop rates for items on the BG Wiki. See here for info:

https://www.bg-wiki.com/bg/Drop_Rate

Splitting the drop rates into six generic categories: guaranteed, common (>50%), uncommon (~25%), rare (~10%), very rare (~5%), and extremely rare, aka lolvoidwatch (<2%).

There's a template for each of them: {{gdrop}}, {{cdrop}}, {{udrop}}, {{rdrop}}, {{vdrop}}, and {{xdrop}}.

Here are a few examples in action:

https://www.bg-wiki.com/bg/Provenance_Watcher
https://www.bg-wiki.com/bg/Ig-Alima

Obviously this is something of a project as it encompasses a huge part of the Wiki (all BCs, monsters, many quests, etc.). We've been missing drop rates on BG Wiki for a long time, and although knowing the exact drop rate of a particular item, like 4.14%, may not be particularly useful information, general and relative drop rates of items is information that we could add in easily as it doesn't require data collection over a long period of time. Feel free to add drop info where it's missing, or edit discussion pages to talk about drop info which you think is incorrect. I think the categories are general enough where it should be fairly easy to pin a particular item's drop rate into one of them.