Spent a little time at lunch today creating a MAC lookup tool for my site. There is now a new menu, Tools, which will have some of the online tools I setup over time.
I use perl script to parse the IEEE oui.txt file and dump it into an SQlite3 database. From there I wrote some PHP to query that database.
You can visit https://techish.net/mac/ and start searching.
The following are all valid formats for supplying a MAC. You can supply the whole MAC if you want, I try to be smart about my filtering.
If you find any bugs, or features, drop me a line.