So here are a couple of things I've done in Seaside that I think are simple yet proved handy.
The first example is from a home financial application that I wrote a few years ago as a way to learn Seaside. My wife and I use it to track our budget and daily transactions, which it imports from a scheduled download done by an iMacro script.
I wanted a bar graph to show how much of the budget for a category was spent for the month. And I wanted parts of the graph to support drilling down for more details. Here is what I ended up with (with some random data)...
...each square is one day of the month. The narrow grey line is to the right of today. If spending in a category is running ahead of the budget, it's red.
The graph is created as a two column table, with the title and the progress bar. The bar is created by rendering same sized (16x16) image buttons, one for each day, and a narrow divider button (3x16) for 'today'.
callback: [self openTransactions];
title: 'Show transactions';
url: TxFileLibrary / #progressredPng
The images were created with Paint.net, a handy tool for simple graphics.
I used a similar approach to create a Kanban graph for an issue tracking system. In this case, a table with fixed sized cells is filled with image buttons representing an issue, to a maximum of five rows. Selecting a cell shows the list of issues for that cell, and the title of each cell shows the display string of the corresponding issue.
I think it's cool what you can due with some dynamic HTML table generation and a few PNG files.