A fantastic solution to scheduling tweets for Twitter is SocialOomph. Mo uses it extensively to automate our tweets, and the billing cycle makes it even more affordable.
SocialOomph allows you to set up different queues called Reservoirs. For tweets that you want to go out on a regular basis, you simply input the tweets into the queue, set up which Twitter accounts you want the tweets to post to, and set the interval between tweets. When you check off "When published, put the update back in the reservoir at the end of the queue." for all the tweets entered, it creates a cycling list within the queue.
Other Twitter scheduling software usually makes you enter each tweet for each day individually, or requires a cumbersome spreadsheet upload. While Mo does recommend always having a spreadsheet to work from (to plan and track your tweets), Mo found uploading is a pain in the neck. And to enter a tweet for 30 days or more was very time-consuming. SocialOomph solved both these issues. Enter it once and forget it!
Also, SocialOomph has a 2 week billing cycle. Instead of paying monthly, they bill you every two weeks, which Mo finds much more budget-friendly. For their current billing rates, click here. You can try it out with a Free trial before you commit to a paid plan.
While the interface isn't "pretty", it works and that's what counts. There is a bit of a learning curve, but it's worth the investment to learn to save precious time down the road.
Another big plus is that you can use it to schedule Pinterest posts.
If you have any questions, or want to share your experiences with SocialOomph, keep reading on how to comment!