To find the mode of the pledge amounts, we first list the individual pledge amounts:
- $6.00
- $5.00
- $5.00
- $5.00
- $3.00
- $7.00
Next, we count the frequency of each amount:
- $3.00: 1 occurrence
- $5.00: 3 occurrences
- $6.00: 1 occurrence
- $7.00: 1 occurrence
The mode is the value that appears most frequently in a data set. Here, the amount that appears most often is $5.00, which occurs 3 times.
Thus, the mode of the pledge amounts is:
\[ \boxed{5.00} \]