This series contains ready-to-use configurations and also all the pieces to make sure you can develop your own custom configurations.
There are arrows that are ready to use: they are one field and the download has a couple of variations. If you need more or fewer arrows, simply add/remove and redistribute along the straight arrow path.
There are also arrow that are two fields: the curved arrow shaft and the arrowhead. You may want to use these versions when developing your graphic because the arrow shafts can be easily aligned with the arrow shaft of the straight arrow - distribute so the are evenly spaced. Then simply add the arrowheads - align and distribute them as well.
The convergence (inflow) and divergence (outflow) concept can be used often instead of a bulleted list. Consider using this layout with a time element as well instead of a gantt chart.
Customizing the arrows
Group the pieces and resize/rescale together. To rescale, hold the shift key down as you resize the group.
Add fill and line colors to any of the pieces except for the arrowhead and curved arrow shaft pieces. If you add a line color to the arrowhead, it will look like it is separate from the curved arrow shaft. Choose colors from your template's color palette or a nice contrasting color.
You will need to use slightly different colors for the converging/diverting arrows than for the straight-path arrow in order for them to appear distinct. You can use color as a coding if you wish: certain arrow colors mean something (via a legend) and other arrow colors mean something else, etc. This is a way to add another layer of information onto the chart.
PowerPoint 2007 options
Drop shadows are okay to use. A shallow-depth bevel might be nice as well to give the arrows some depth.
Shallow-depth 3D arrows can be okay to use, although the arrows don't appear to converge with the straight path arrow – instead, they appear to be layered on top of the straight path arrow. This might be your message: a gathering for forces, etc. Make sure that the formatting you use does not contradict your primary message. Nuances are very important with graphics.
Drop shadows (PowerPoint 2007 and 2010) lift objects off of the page. As with 3D, make sure that you use them carefully. Shadows tend to make things distinct and separate, which may not suit a convergence-type concept.
Gradients, patterns, and pictures
Gradients can be tricky because of the curve. Try a few and see if the effect is suitable. Imported pictures may work if the design, subject can still be apparent after importing it into the arrow(s).
Simple reveals work best with curves like this.