Zamzar is a free tool that works online, without requiring any special program to be installed. Even though it is a bit slow, the conversion is excellent, and your final JPG files will not lose out on image quality.
The best thing is that it detects many RAW formats like NEF, RAF, CR2, DNG etc., but you can convert files of only 50 MB for free. Also, using a free account here means converting only two images within twenty-four hours.
To convert images using Zamzar, upload the CR2 file, choose the output format as JPEG, and click the Convert button.

My overall rating: 4   

Convertio is a powerful online service that recognizes many RAW formats and converts them into JPGs. Like Batch Picture Resizer and Zamzar, you need to upload your CR2 file, select the format you want and let the tool do the rest!
Besides image conversion, Convertio also converges audio files, videos, documents and PDFs. Since the conversion happens on the servers of Convertio, even an old computer will be able to use its features easily.

My overall rating: 4.5   

Image.Online Convert is a simple website that allows you to upload a RAW and convert it into JPG.
Although it does not have a lot of fancy features, it lets you select the level of compression – none, low, medium, high and best. The higher the compression level, the lesser the file size, although your image might suffer slightly in quality.
You can also select the exact image size by entering the width and height image resolution and changing DPI, which is a helpful setting if you want to print your photos.

My overall rating: 3.5   

If used with GIMP, UFRaw becomes a powerful tool because it lets you edit images using layers, healing, clone stamp, curves, and more. And the best thing – it is completely free!

3   

Like Photoshop, Aftershot Pro is a image editor that can be used as a CR2 to JPG software. Although it needs a subscription, it will be a one-time investment because Aftershot can handle all your RAW photos from start to end.
It provides batch conversion, too, so you can select multiple CR2 files and convert them together. You get lens correction, blemish removal, levels and curve adjustments, and conversion!

4.5   

4   

Preview is a photography program already installed in your MAC device, and can be used to convert RAW image file easily.
While the thumbnails for your RAW photo won't be displayed, you can right-click any CR2 file and select Open with Preview. Go to File > Export, and select JPG as the final output image format. You will see a converted JPG in the folder once you click on Save.
Since Preview is already built-in, this method doesn't require downloading any other software!