Incell graphs in Excel
You can do a lot of things with Excel. Sometimes it's pretty; sometimes it's not. Sometimes the users come up with better solutions than the developers. Let's have a look.
The trail
 Microsoft Excel 2007 (nee Excel 12): Conditional Formatting  overview of what we did, and what's a "data bar"?
 shows off Excel's new "data bars"  a sort of incell bar graphs. A good idea, but poorly executed. The bars extend _behind the text_, and the gradient fills makes it even harder to get a decent overview of the values they represent.
 [Juice Analytics: Lightweight data exploration in Excel](http://www.juiceanalytics.com/weblog/?p=236) (via [Lifehacker](http://lifehacker.com/software/top/exceltipinstantincellgraphs193425.php))
Excel _users_ have found a rather ingenious way to make _better_ data bars than the Excel team did, by using the `REPT` function to repeat the bar character (""), resulting in a rather visually pleasing incell graph variant.
Some creative commenting ensues, thus leading to...
 [Juice Analytics: More on incell graphing](http://www.juiceanalytics.com/weblog/?p=239)
 with examples of various enhancements, including a demo spreadsheet for download (much to my delight, OpenOffice Calc handles it brilliantly, too).
A few tweaks
After a bit of toying around with examples, I ended up tweaking it a bit:

Instead of dividing values by a constant (to get the numbers of bar characters to use), I divide by
MAX($G$2:$G$32)
(G2:G32 being the relevant cell range), and multiply by the maximum number of bars I want. 
Low values may result in no bars at all, even though the value isn't strictly zero. I use
CEILING
to round the above value to the nearest larger integer, making all positive values get at least one bar. 
Using a lowercase "o" for dot graphs is cute, but using a bullet ("•") is better. Insert it as a special character (U+2022) or, on windows, by holding down alt while typing 0149 on your numeric keyboard. They can also quite favorably be used instead of the bar character for barlike charts.
Various links
The obvious connection here is Sparklines, Edward Tufte's "Intense, Simple, Wordsized graphics". Infographics make my fingers tingle.
 Bissantz sparkline tools uses a special font to generate sparklins graphics just about anywhere.

A Google search for sparklines reveals all you need to know about them, including sparkline generation libraries for various programming languages.

This is apparently what Excel 2007 looks like. Just slap a Hello Kitty sticker on there somewhere, and you're done. (Oh, look, there's another "skin" available too! Because, y'know, you can never have enough of interuser inconsistencies in the interface.)
 Sander Viegers, Excel User Experience Designer talks about part of the process behind some charting improvements in Excel 2007. I like the paper sketches best.