Can I uninstall stock Apple applications (e.g. Stickies)
Yes, technically, you can, but you shouldn't.

Reasons you shouldn't:


Apple will sometimes update the applications in minor OS upgrades. As the rest of the application isn't there, you end up with only the files that were changed. 
What if you decide you need them in the future? You'll have to reinstall the OS.
On Snow Leopard and later, the apps you mention take up almost no space - Mail is a measly 77 megs.


If you do decide to delete them, it's easy: drag them to the Trash or hit Command-delete just like any other file. Do make a backup before you delete things, and do also test the apps you delete or trim right away. You want the Mac to crash now while you remember what you deleted.

Be hesitant to delete Image Capture or TextEdit. The former controls scanning and importing pictures from any device and the latter is called for in some cases if you need to edit a system file. I'd also say leave Mail around - especially if you ever will set up a guest account and let someone use your Mac for a short amount of time.

You probably won't hose up too much with the rest. I should mention again that this is very much discouraged because it breaks the system that tracks what software was installed. Software installed by Apple gets recorded in a receipts database, and these receipts don't contemplate a partial uninstallation and you are gambling that there isn't a connection between these apps and others you may need later.

Why not look elsewhere to save some space? You can and should look in /Library/Application Support and delete some of the iDVD loops and Audio Loops for GarageBand. Also, compare the size of all the apps you intend to clean out and compare it to one music video or a few songs in iTunes. You probably can find much better targets to free up substantial space rather than getting rid of some essential system utilities that take up little to no space in reality.