My go to for tongue twisters:
https://spiritsound.com/music/twisters.html
Accents help:
https://www.dialectsarchive.com/comma-gets-a-cure
Finding projects:
https://www.castingcall.club/
Example scripts for practice:
https://www.voicereels.com/scripts/
https://edgestudio.com/scripts/
https://www.ispot.tv/ad/top-commercials
Reducing mouth noises
https://voiceactor.com/articles/techniques-reducing-mouth-noises-when-recording-voiceovers
Voice Acting Club is a great resource in general:
https://voiceactingclub.com/
https://voiceacting.boards.net/thread/5286/get-started-voice-acting