Barry Bonds hit his 40th homer of the year and the 698th of his career tonight. He has now hit 40 or more in each of the last five seasons. That's the fourth longest such streak in baseball history, but it's not even good enough for second best among current streaks.
Both Alex Rodriguez and Sammy Sosa have a six-season streak going. Babe Ruth hit 40 home runs in seven consecutive seasons (1926-32), the longest streak. A-Rod currently has 33 and projects to 39, so he has a decent shot of matching Ruth. Sosa, however, has just 29 dingers which projects to 35. Unless he hits a very hot streak, his streak will end.