COUNT
Formula: =COUNT(A1:A10)

The count formula counts the number of cells in a range that have numbers in them.

LEN
Formula: =LEN(A1)

The LEN formula counts the number of characters in a cell. Be careful though! This includes spaces.

TRIM
Formula: =TRIM(A1)

Gets rid of any space in a cell, except for single spaces between words.

NOW Returns the system date and time

TODAY Returns the system date, without the time

SUMIF Calculates a sum from a group of values, but just of values that are included because a condition is met

COUNTIF Counts the number of cells in a range that match a criteria

You can find more formulas infact all the formulas in excel itself.

From the menu bar select "FORMULAS" and then choose your formula which is categorised in various headings.