I'd have to say Hackvertor (disclaimed I wrote it) it's free and it supports tag based conversion. Check out the example:-
http://www.businessinfo.co.uk/labs/hackvertor/hackvertor.php#PEBoYXNlZ2F3YV83KCKqwMHCw8TGyMnKy8zNzs%2FQ0dLT1NXW2Nna29zd3t%2Fg4eLj5OXm5%2Bjp6uvs7e7v8PHy8%2FT19vj5%2Bvv8%2Ff4kXyIpPmFsZXJ0KCJJJ2Qgc2F5IEhhY2t2ZXJ0b3IiKTxAL2hhc2VnYXdhXzc%2B
