Kirikae by Lance Fetters provides a pop-up list that can be used to switch to/launch other applications without having to return to SpringBoard
Changes in version svn.133: NEW: Added "Use Large Rows" option; disable for new, smaller rows. * Note that when using smaller rows, badges are enlarged to increase legibility
NEW: Added "Use Themed Icons" option; disabling will prevent use of WinterBoard-themed icons. * This is especially useful for those using themes with unusual-sized icons.
FIX: Fixed ability to quit Mail/Phone when using firmware >= 3.1.
MOD: Active tab: * Replaced swipe-to-quit behavior with always-visible quit button. * Quitting the current app will no longer close Kirikae. * springBoard is now always shown at the top in "Home Screen" section. * Renamed current/other applications to foreground/background * Applications. * "Foreground Application" section is only shown if not SpringBoard. * "Background Applications" section is now sorted by most-to-least recent usage.
You can find Kirikae in the Big Boss Cydia Repository.