There are several web-based plotting and data visualization tools available, each with its unique features and capabilities. The best one for you depends on your specific needs and preferences. Here are some popular web-based plotting software options:

1. **Plotly (plotly.com):** Plotly is a versatile data visualization tool that supports a wide range of chart types. It's known for its interactive and web-friendly visualizations. You can use it in Python, R, or JavaScript. It offers both open-source and cloud-based versions.

2. **D3.js (d3js.org):** D3.js is a powerful JavaScript library for creating custom data visualizations. It provides a lot of flexibility and control over your visualizations, making it suitable for developers who want to build unique and interactive charts.

3. **Highcharts (highcharts.com):** Highcharts is a JavaScript charting library that specializes in creating interactive and aesthetically pleasing charts. It's commonly used for business and financial data visualization.

4. **Google Charts (developers.google.com/chart):** Google Charts is a simple and free tool that allows you to create a variety of charts using a JavaScript API. It's easy to use and suitable for basic charting needs.

5. **Chart.js (www.chartjs.org):** Chart.js is a lightweight JavaScript library for creating responsive and easy-to-use charts. It's a great choice for adding simple, interactive charts to web applications.

6. **Matplotlib (matplotlib.org):** While Matplotlib is a Python library, there are web-based interfaces that allow you to create, customize, and save charts directly in your browser. Matplotlib is well-known for its static, publication-quality plots.

7. **Tableau Public (public.tableau.com):** Tableau Public is a free version of the Tableau data visualization software. It's excellent for creating and sharing interactive visualizations. Note that while it's free, visualizations are public by default.

8. **ChartBlocks (chartblocks.com):** ChartBlocks is an online tool for creating charts and graphs. It offers a drag-and-drop interface, and you can export your charts in various formats.

9. **Infogram (infogram.com):** Infogram is a data visualization tool that focuses on creating infographics, charts, and maps for storytelling. It's often used for presentations and reports.

10. **Gnuplot (gnuplot.info):** Gnuplot is a command-line-driven tool for creating 2D and 3D plots. While it's not web-based, there are web interfaces available that allow you to generate Gnuplot graphs and view them in your browser.

When choosing a web-based plotting software, consider your data visualization requirements, the level of interactivity you need, the programming languages you are comfortable with, and whether you prefer a free or paid solution. Many of these tools offer free trials or open-source versions, so you can experiment and find the one that best suits your needs.