Since I have been homeschooling since 1998, I often get asked by new homeschoolers what curricula that I recommend. There are so many good ones out there, but I'll give you a list of the basics that are my #1 choices.
Math: Christian Light Math is my top pick after years of trying to find a program that explained concepts well, had enough review, didn't require tons of additional purchases, was inexpensive, academically challenging and worked for all my kids. This program starts at 1st grade and goes through high school. Be sure to use the Sunrise editions. Most of the program has been updated, but the high school level books are currently in revision.
Grammar: Rod and Staff Grammar is easy to use, gets the job done, reusable, and prepares your child for college level work. It includes grammar & writing exercises. We tried other programs but they were often confusing, lacking in depth or too cutesie. I recommend this completely. Neither of these programs are flashy, but they are the best in my opinion. We save the flashy for other subjects. This program starts at 2nd grade (we skip this one) but you don't really need to start it until 3rd.
Handwriting: Pentime - This gem of a program is the best kept secret out there. The workbooks are inexpensive (around $5) but high quality paper and print. The content is excellent. I believe once the child gets to the 3rd book, every lesson has a copywork selection based on the books theme. My favorite themes were the bird book and the States book. Two books are available for 1st grade (use one in K?). After that it is one book per grade, no teachers manual. It goes up to grade 8.
History: Heart of Dakota - Starting in about 3rd grade, I highly recommend Heart of Dakota Preparing Hearts for His Glory. I am not a fan of the programs before this one, but I am a fan of all the ones that follow. Heart of Dakota includes all subjects but you can use any of the above easily in place of the scheduled ones. We have used nearly all of this company's programs.
Science: R.E.A.L. Science Odyssey If your not using Heart of Dakota, you may want to check out the fun science programs offered by Pandia Press. We used the Earth and Space one along with Apologia's Astronomy book which was a great combination. The experiments are easy, fun and educational. My kids loved it when we had science each week. To make things easier, I purchased a kit from Home Training Tools with most of the supplies needed to complete the experiments.
This list is not exhaustive and I post more favorite programs in upcoming posts. Happy curricula shopping!