If you don't want to listen to full symphonies you can listen to some symphonic poems - They're good if you're not in the mood for a full symphony.
Good symphonies:
- Tchaikovsky's 4th, mvt 1 and 4.
- Tchaikovsky's 3rd, mvt 4.
- Tchaikovsky's 5th, mvt 1.
- Tcahikovsky 6th, mvt 1. (What can I say, he rocks.)
- Rachmaninoff's 2nd, mvt 3.
- Saint-Saens' 2nd mvt 4.
- Dvorak's 9th, mvt 1 and 2.
- Schumann's 4th, mvt 2 and 3.
- Grieg's symphony in C minor, mvt 1.
- Brahms' 4th, mvt 1 and 3.
- Brahms' 3rd, mvt 1 and 4.
- Mahler's 2nd, mvt 1.
- Gliere's 3rd, mvt 4.
- Wanger's 9th, mvt 2.
There are about a thousand more. Also, I truely recommend listening to the entire symphonies whenever you have the chance, they're as good as music gets.