These are some plotting programmes for scientific plotting and curve fitting which can be used without programming / coding. They are free software:

- Veusz: https://veusz.github.io/
- Labplot: https://labplot.kde.org/
- Fityk in particular for fitting and processing of spectra: https://fityk.nieto.pl/
- LibreOffice, the free office suite, also includes a tool for making diagrams and fits: https://www.libreoffice.org/

 

Free software packages for data analysis including plotting:

- GNU Octave, language for numerical computations (graphical user interfaces exist): https://www.gnu.org/software/octave
- R, free software for statistical computing and graphics (graphical user interfaces exist): https://www.r-project.org/
- python, a programming language easy to learn which comes with *many* data analysis packages: https://www.python.org/
- maxima (incl. GUI wxmaxima) is a traditional computer algebra system: https://maxima.sourceforge.io/

 

The following is a list of "new" software for statistics, visualisation or machine learning. Most of them is open source / F(L)OSS. Try it out and let me know if you can recommend it:
- Visualization program for exploring high-dimensional data: http://www.ggobi.org
- Visualize data using an online graphical user interface (GUI) that makes use of R's visualization package ggplot: https://github.com/gertstulp/ggplotgui
- Data visualization framework with the goal of making the visual representation of complex data easy: https://rawgraphs.io/
- A new statistical spreadsheet, easy to use, built on top of R: Jamovi (https://www.jamovi.org/)
- Statistics framework: JASP (https://jasp-stats.org/)  
- Data Mining, machine learning and data visualization, data analysis workflows visually, with a large, diverse toolbox: https://orangedatamining.com/
- A collection of machine learning algorithms for data mining; tools for data preparation, classification, regression, clustering, association rules mining, and visualization:  Weka (https://www.cs.waikato.ac.nz/ml/weka/index.html)  

 

Live data visualisation
- Trend graph for “live” data; data is displayed in real-time into a multi-pass trend (much like a CRT oscilloscope): https://www.thregr.org/~wavexx/software/trend/
- Grafana, a visualisation and analysis platform: https://grafana.com/

The last group is probably the opposite of a plotting program, it allows you to digitise data:
- xyscan
- PlotDigitizer