There are so many great online resources for spelling! I use a mix of Home Spelling Words and Spelling City. I use the lists from Home Spelling Words and then put them into Spelling City so that the kids can play games with the words and hear the definitions.
Spelling City 
Spelling City  is an easy-to-navigate site for finding pre-made spelling lists. You can print out the list or you can let your child do it online. There are games and printable handwriting practice sheets, as well. There is also a paid version, but the free version really has a lot to offer too.
Home Spelling Words  offers basic word lists & tests for grades K-7. You can also add your own lists! It also keeps tests scores and a grade report. This looks like it might work for kids who get distracted by lots of colors and flashing lights on the screen. It’s a basic, easy to use (with tutorials if you need them) program.
The Basic Cozy Spelling Course  is offered for free from Splashes from the River. It is for ages 9 & up, as you will see if you check out the word lists. This is a course that is designed to go in a specific order, so if you pick and choose lessons, you might miss out on something. It has word lists and dictation sentences for applying context to the list words.
Garden Of Praise 
Garden of Praise has Bible-based spelling lessons  as well as some musical spelling lessons  complete with MIDI files to accompany you. This really is a garden of resources for homeschool parents. Browse around and see if there is something else you might use.
Eduction.com has hundreds of spelling lessons. No registration is required, just click and spell. They have guided lessons, lesson plans, printable worksheets, online games, and more for grades kindergarten through fifth.
If you are more inclined to skip the online lessons and get back to basics, try the Charlotte Mason style of learning spelling rules while doing copy work. SimplyCharlotteMason.com  describes how to use living books, classics, or your normal textbooks to use “prepared dictation” to introduce spelling & vocabulary.
Discovery Education 
You can use this Puzzle Maker page  to create fun word game printables while using your own lists. For example, if you are doing a literature unit from Garden of Praise on the Boxcar Children Books , you can take the phonograms (rhyming word families) listed and make a puzzle out of them. Some kids won’t even know they are learning!
Master Spell  administers spelling drills using over 3,600 included words and sentences spoken with a real voice and supplemental guidance using the Mac’s Text-to-Speech. Parents and teachers can record their own words and sentences too.