Three nights in Athens, and two day trips
 

Looking for a mid-priced hotel in Athens for mid-September. Nice but not essential that it is fairly near Mets, since that is where the Half Note Jazz Club is, and I'll be there each evening. Small and out of the way places are especially welcome. Also, we have two days free for day trips. Thought one might be out to Hydra plus another close-by island. Very open to suggestions about the other day trip. Thoughts? (It's our first time there and we are retired Aussies).

With only 3 nights in Athens, you might want to use your days to explore the city itself, as Athens holds an incredible array of wonderful sites.

If leaving the city is your priority, where to go would really depends on your interests, but Delphi would be high on my list of options.

Mets is in top centre of Athens and a very desired small neighbourhood for most Athenians :)
Ah and Half Note is my favourite Jazz Club in Athens and one of he oldest ones !!
You will find plenty of Hotels just across the gardens of Olympieion and Hadrian's Arch, they are a short stroll away from Mets.
All hotels located near the Acropolis Metro Station or even Syntagma Square are in the vicinity of Mets.

Excellent suggestions, thanks. Actually we are planning on heading out of town rather that seeing too many of the city sites. Wife HATES big cities, but I will check out a couple of essential spots in the city on my own.

Stayed at the Hera hotel. Excellent location and hotel

I am currently in Athens and loving it. This is our second time here and there is alot to see. That being said, I concur that Delphi would make an excellent day trip if you would like to see amazing ruins.

You may be able to pair this with visiting the ancient monestaries of Meteora but that would be a two day trip.

If you are interested in visiting a nearby island, I would suggest a three island cruise which you can book through any travel agent once you are in Athens. It had been our intention to visit Hydra and Aegina on two separate days, but were convinced to take a tour to Hydra, Aegina, and Poros all on one day. Since each island can be seen in a short time, this worked out perfectly for us. We were picked up today at 7:15 from a close by hotel and returned at 7:00 pm. The day included a very nice buffet lunch, as well as Greek music and entertainment on board. Alternatively, you could sit outside on deck and relax watching the water.

Whatever you end up doing will be wonderful. Enjoy!