Yes - it is possible to do many agile practices as an individual.
If you already know how to do these, you can do them as a sole developer:
- test-driven development - great place to start
- refactoring
- continuous integration
- doing the simplest thing that could possibly work (and evolving it through refactoring)
- automated deployment
- planning meetings (a team of one plus customer)
Things you can't do on your own:
- pair programming
- CRC/RRC workshops (... you'd have to talk to yourself quite a lot)
