If you've just started I2P, the Active: numbers on the left should start to grow over the next few minutes and you'll see a "shared clients" local destination listed on the left (if not, see below). Once those show up, you can:

• browse "eepsites" - on I2P there are anonymously hosted websites - tell your browser to use the HTTP proxy at 127.0.0.1 port 4444, then browse to an eepsite:
  
  • forum.i2p: a secure and anonymous connection to forum.i2p2.de
  • www.i2p2.i2p and mirror i2p-projekt.i2p: secure and anonymous connections to www.i2p2.de
  • eepsites.i2p: an anonymously hosted search engine of eepsites
  • ugha.i2p: ugha's eepsite, a wiki that anyone can edit, and lots of links
  • fproxy.tino.i2p: Freenet proxy
  • echelon.i2p: software archive (I2PFox, iMule, I2P-Messenger, ... ) and information for I2P
  • paste.i2p2.i2p: secure and anonymous paste service.
  
  There are many more eepsites - just follow the links from the ones you see, bookmark your favorites, and visit them often!
• browse the web - there is currently an HTTP "outproxy" in I2P hooked up to your own HTTP proxy on port 4444 - simply set your browser's proxy to use it (as above) and go to any normal URL - your requests will be bounced through the I2P network.
• transfer files - there is an integrated port of the Snark BitTorrent client.
• use anonymous email - postman has created a mail system compatible with normal mail clients (POP3 / SMTP) that allows email within I2P as well as mail from and to the normal internet! get your account at hq.postman.i2p. We bundle susimail, a web based anonymity-oriented pop3/smtp client configured to access postman's mail services.
  Alternatively, you can try out our new serverless, end-to-end encrypted e-mail system I2P-Bote (with webinterface), installable as a plugin.
  
• chat anonymously - fire up your own IRC client and connect to the server at 127.0.0.1 port 6668. This points at one of two anonymously hosted IRC servers, but neither you nor they know where the other is.
• blog anonymously - check out Syndie
• and lots more

Want your own eepsite?

We've bundled some software to let you run your own eepsite - a Jetty instance listening on http://127.0.0.1:7658/. Simply place your files in the eepsite/docroot/ directory (or place any standard JSP/Servlet .war files under eepsite/webapps, or standard CGI script under eepsite/cgi-bin) and they'll show up. After starting up an eepsite tunnel pointing at it, your eepsite will be visible to others. Detailed instructions for starting your eepsite are on your temporary eepsite page.

Troubleshooting

Be patient - I2P may be slow to start the first time as it searches for peers. If, after 30 minutes, your Active: connected/recent count has less than 10 connected peers, you should open I2P's port on your firewall for better connectivity. If you cannot see any eepsites at all (even www.i2p2.i2p), be sure your browser proxy is set to 127.0.0.1 port 4444. You may also want to review the information on the I2P website, post up messages to the I2P discussion forum, or swing by #i2p-help, #i2p or #i2p-chat on IRC at irc.freenode.net, irc.postman.i2p or irc.freshcoffee.i2p (they're linked together).