You can also put the frozen water bottles or cold packs in front of a fan for "redneck A/C".
A few weeks ago my husband and I installed UV-blocking film on our south-facing windows to help keep the house cooler, and I could tell the difference almost immediately in those rooms. I expect that to pay for itself quickly in lower electric bills. This is the product we purchased: https://www.amazon.com/EXTERIOR-Wind...dp/B00VH01FGA/