When we first started homeschooling several years ago, my kids didn't know their months very well, and they especially didn't know the numbers associated with each month. So after fruitlessly searching on the internet for some worksheets, teaching ideas, etc., I came up with my own to help my kids learn their months (and their numbers).
Here's a link to all five worksheets in one document if you'd like to download them for your own use (just click the link to download).
I started out with this simple printout of the months, broken down into seasons. I went over the sheet with the kids as an introduction, but I didn't necessarily require them to memorize it at first as I expected (hoped) the drills to really solidify the numbers in their heads better than rote memorization.
Then I showed them another handout that broke the months down into quarters.
I had my kids memorize the months and the associated number (one quarter at a time), and then do the exercises on this first worksheet (see below), which covers months 1 through 6.
The above worksheet is broken down into stages so my kids only had to memorize three months at a time. Exercises 1 & 2 on the worksheet covered the first quarter (Jan-Mar), exercises 3 & 4 covered the second quarter (Apr-Jun), and then exercises 5 & 6 covered both quarters together.
On the worksheet, when the month was listed, they would put the associated number next to it; when a number was listed, they would write the first three letters of the associated month. (I had the kids write just the abbreviation, otherwise they'd get quickly tired of writing the month in full and miss the main point of the exercise!)
The worksheet below covers months 7-12 in the same manner as the last worksheet. Months 7 through 9 are covered first, then 10 through 12, and then all six months are reviewed in exercises 5 & 6.
This last worksheet is simply a before and after exercise. I had my kids write the first three letters of the month that comes before or after the month listed, depending on the position of the blank line. This worksheet covers all twelve months of the year.