With CloudMade changing their API to focus on enterprise customers, I had to find an alternative for hosted map tiles.
Instead of the old CloudMade tile tutorial used on Leaflet:
attribution: 'proper attribution goes here'
You can use Open MapQuest:
attribution: 'proper attribution goes here',
subdomains: ['otile1', 'otile2', 'otile3', 'otile4']
Just make sure your attribution properly reflects all your sources.