Adobe Photoshop and Adobe Illustrator are awesome...I would definitely recommend getting to know these 2 if you're getting into graphic design...they're tons of fun too!
You can also use flash to make banners, but you'll need some other software like Photoshop to edit any bitmap images, before they're imported
I try photoshop but the interface is so confusing But I find corel draw very good and the GUI is much more user friendly
a lot of collections out there if you want..the FREE one and the paid one. For paid version used Photoshop,Illustrator or Flash.That the best software so far I know. FOr FREE version try to use Gimp or Inkscape to make your own banner ads the best way to design it and get the better result,hire designer to design yours or hold a contest to make your banner..that's all from reezluv...
I use Photoshop, Illustrator and Flash for all my graphics. You can get the Adobe CS3 Design Premium Suite for about $1800. Seems like a lot of money... but it'll easily pay itself off over time.