General (including subjects and behaviors/work habits)
Education World's 100 Report Card Statements (attitude, behavior, work habits, social skills, time management. These are all written in positive language so if you have to show where student needs to improve, you can just make the necessary changes)Easy Report Cards - comments by grade and also by subject
Report Card Comments - for a variety of specific classes
Actual teacher's report card comments for Grade 4 - by subjects and strands
Sample Report Card comments
Report Card Comments - negative and positive
Elementary Report Card Comments
Over 125 Free Report Card Comments
101 Report Comments to Use Now (Scholastic)
Report Card Comments
Comment Ideas for Report Cards and Progress Reports - TeachNet
Lakeshore Learning Report Card Comments
100 Useful Words & Phrases When Writing Report Card Comments For Elementary Students
K-8 Report Card Comments
Literacy/Language Arts
Literacy (Language) Report Card StatementsReport Card Comments for Language Arts
Math
Comments for Math (About.com)Physical Education
PE Report Card Statements
Grading and Report Cards for Standards-Based Physical Education towards the middle to the end it has some nice comments and standards that can be used
Science/Social Studies
SuperTeacher Worksheets Social Studies and Science Report Card CommentsReport Card Comments for Social Studies (K-6 Educators.About.com)
Report Card Comments for Science (About.com)
Other Ways to Use Report Card Comments:
As I was browsing these resources I thought that many of the comments can be used to set student goals or as topics for mini workshops to teach various skills even if you don't utilize grading in your homeschool.