Follow up latest research results:

• International Association of Synesthetes, Artists, and Scientists (IASAS)
• UK Synesthesia Association
• American Synesthesia Association
• German Synesthesia Association

Tests:

• synesthesia.com; blog and tests
• synesthete.org; Synesthesia battery; platform for testing synesthesia by David Eagleman laboratory

Literature & Magazine:

• Synesthesia Magazine, magazine about art and crossed senses

Art:

• Melissa McCracken, synesthetic painter