There are apps for taskbar functionality but the two I tried didn't seem to work.
However, there are (undocumented, of course
) shortcuts.
Click-and-hold the back button will on *some* apps offer up a dialog box to choose between minimizing and closing the app.
Clicking Home will usually take you to the home screen.
Click-and-hold on the home button will offer up a box with recently open apps and (if the app is still running) tapping on its icon will switch back to it.
Just don't expect consistency.
These shortcuts only work when they work.