Past record on MLB over/unders:

2009: 8-4
2008: 2-7
2007: 7-1
2006: 2-1

Total: 19-13

For 2010:
4 units - Cardinals over 88.5
4 units - Astros under 74.5

3 units - Dodgers over 84
3 units - Cubs under 82
3 units - Angels over 82.5

2 units - Blue Jays under 71
2 units - Pirates under 70.5
2 units - Mets under 81
2 units - Braves over 85.5
2 units - Athletics under 80
2 units - Diamondbacks over 82.5

1 unit - Twins over 82.5
1 unit - Tigers over 80
1 unit - Indians under 75.5

For more over/under talk, go check out Pete Schoenke's column and Joe Sheehan's column, and please offer your own leans in the comments.

Line source: Pinnacle.