Children need to feel confident skip counting in order to learn their basic math facts.

HomeschoolMath.net
Counting by 2, 5 and 10s @ HelpingWithMath.com

Here is a lesson and online practice to learn skip counting from the website

MathIsFun.com.

Here's a simple fun song to memorize to teach skip counting. It is taken from fun.familyeducation.com

Skip counting dot to dot worksheets @ ABCTeach.com

Here'a game that will help you skip count just about any number @ AmbleSidePrimary.com.
Online games about skip counting @ FreeHoldTWP

AToZTeacherStuff.com
Counting by 3s with a joke

Skip counting poem activity. (You will need a handout with skip counting numbers on it.)

Skip Counting Game

Learning to count by twos, fives, tens, fifties, and hundreds will make basic arithmetic easier for your child. Before you begin playing, learn the skip-counting jingle and its rhythmic accompaniment:

Directions

(slap knees) (clap hands) (snap left hand) (snap right hand)
Counting, counting, 1, 2, 3.
That's too easy, can't you see?
Count in- stead by twos or threes, or
By the number named by me.

The players sit in a circle on the floor.
To begin, they recite the jingle together while slapping, clapping, and snapping as shown above.
All the players continue to slap, clap, and snap as the first player declares a number to count by (for example, ten).
The player to his left then must say the next number in the series (in this case, twenty).
Play continues around the circle.
Each player must say the next number in the series during one slap-clap-snap-snap pattern.
If a player is stumped or says the wrong number, he must drop out.
To resume the game, the remaining players recite the jingle again and declare a new number.
The last player remaining after all the others have dropped out is the winner.