Instiki
Tikz

Tikz has become the de-facto standard for producing figures in TeX. It’s more concise than SVG. On the other hand, it doesn’t have the advantage of a WYSIWYG tool for creating it. Still, many TeX aficionados swear by it. So Instiki 0.30.0 supports it.

Here’s an example of some Tikz code

\begin{tikzpicture}[decoration={markings,
mark=at position .5 with {\arrow{>}}}]
\usetikzlibrary{arrows,shapes,decorations.markings}
\begin{scope}[scale=2.0]
\node[Bl,scale=.75] (or1) at (8,3) {};
\node[scale=1] at (8.7,2.9) {$D3$ brane};
\node[draw,diamond,fill=yellow,scale=.3] (A1) at (7,0) {}; 
\draw[dashed] (A1) -- (7,-.7);
\node[draw,diamond,fill=yellow,scale=.3] (A2) at (7.5,0) {}; 
\draw[dashed] (A2) -- (7.5,-.7);
\node[draw,diamond,fill=yellow,scale=.3] (A3) at (8,0) {}; 
\draw[dashed] (A3) -- (8,-.7);
\node[draw,diamond,fill=yellow,scale=.3] (A4) at (8.5,0) {}; 
\draw[dashed] (A4) -- (8.5,-.7);
\node[draw,diamond,fill=yellow,scale=.3] (A5) at (9,0) {};
\draw[dashed] (A5) -- (9,-.7);
\node[draw,circle,fill=aqua,scale=.3] (B) at (9.5,0) {};
\draw[dashed] (B) -- (9.5,-.7);
\node[draw,regular polygon,regular polygon sides=5,fill=purple,scale=.3] (C1) at (10,0) {}; 
\draw[dashed] (C1) -- (10,-.7);
\node[draw,regular polygon,regular polygon sides=5,fill=purple,scale=.3] (C2) at (10.5,0) {};
\draw[dashed] (C2) -- (10.5,-.7);
\draw (6.8,-.7) -- (6.8,-.9) to (9.2,-.9) to (9.2,-.7);
\draw (9.8,-.7) -- (9.8,-.9) to (10.7,-.9) to (10.7,-.7);
\draw[->-=.75] (C2) to (10.2,.35);
\draw[->-=.75] (C1) to (10.2,.35);
\node[scale=.6] at (9.9,.35) {$(2,2)$};
\draw[->-=.7] (B) to (9.6,.7);
\draw (10.2,.35) to (9.6,.7);
\node[scale=.6] at (9.35,.9) {$(4,0)$};
\draw[->-=.5] (9.1,.8) to (A5);
\draw (9.6,.7) to (9.1,.8) to (A5);
\draw (9.1,.8) to [out=170,in=280] (8.3,1.45);
\draw[dashed] (8.3,1.45) to (8.1,2.5);
\draw[->-=.5] (8.1,2.5) to (or1);
\node[scale=.75] at (7.7,2.7) {$(3,0)$};
%\draw (11.4,2.4) to [out=180,in=90] (6.2,-.5) to [out=90,in=0] (or1) -- cycle;
\node[scale=.75] at (8,-1.1) {A-type};
\node[scale=.75] at (9.5,-1.1) {B-type};
\node[scale=.75] at (10.25,-1.1) {C-type};
\draw[dashed] (8.7,.6) to [out=180,in=90] (6.2,-.55) to [out=270,in=180] (8.7,-1.6) to [out=0,in=270] (11.2,-.55) to [out=90,in=0] (8.7,.6) -- cycle;
\node[scale=1] at (12,.6) {$E_6$ singularity};
\end{scope}
\end{tikzpicture}

which, when processed, produces

Setup

To enable Tikz support in Instiki, you need to do two things

1. Install a tex2svg server, either on the same machine or on one that Instiki can contact over the network.
2. Uncomment the last line of config/environments/production.rb, which gives the URL for the tex2svg server (defaults to http://localhost:9292/).

Now you can embed Tikz code on your Instiki pages and have it rendered to SVG by the tex2svg server.

It should be noted that there is an accessibility downside to using Tikz, rather than SVGEdit to create your figures: all text is turned into outlines, which makes the result completely (instead of merely mostly) inscrutable to screen readers.