I've been building MCPJam, an open source LLM chat playground for MCP servers. It's a MCP server testing tool, like Postman for MCP servers. You'll learn a lot about building LLM clients, working with React, Hono, Vercel AI SDK, lots of AI product engineering concepts.
If you're interested in contributing, or checking out the project, here's the GitHub:
https://github.com/MCPJam/inspector
To start, you can take a look at the Issues tab and see if there's anything there that interests you. Easy tasks are labelled "good first issue". Leave a comment in the issue if you're interested in taking it on!