Take a second and examine your own playstyle. You may not realise it, but you'll have settled into a routine; it's only natural – any new parent will tell you that routines are essential – they let us know where we are, and they allow us to plan our time constructively. I would imagine most 'casual' players have much the same routine as I do, but it struck me recently that routines can just as easily be a bad thing – my routine is such that I honestly struggle to remember the last time I stepped foot in an instance.
There's nothing wrong with stepping out of your comfort zone and trying something different for a change every once in a while. As important as a good routine is, it's just as important to mix things up and keep your gaming fresh; otherwise you run the risk of burning out sooner than you think; not because you've seen everything there is to see, but out of sheer boredom.
I happened to have Tuesday off, so I logged on with one of my level 70 characters, joined the LFG channel and started offering my services, free of charge, to boost lowbies in any old-world dungeon they wanted. About 30 seconds later, I had a group organised and spent the next hour clearing out the Sunken Temple, and I had a blast. Not only did I feel super-cool because I was ridiculously overpowered for the instance, but I felt a warm fuzzy glow for helping out some random strangers. I can't recommend it enough – spread some good Karma around, and run a lowbie through an instance – at level 70, you'll fly through it, and it won't take too long either.
There are a couple of other things you could try, PvP for one. PvP isn't for everyone, myself included, but it can make an entertaining alternative to your usual online escapades. Over the weekend, I grabbed Exteel from NCSoft and spent a couple of evenings of raw, mech-based PvP goodness. The game is free to play, easy to get the hang of, and seems well suited to short, sharp bursts of gaming. Alternatively, try PvP in your main game – I don't really spend much time in the Battlegrounds, but I jumped into Warsong Gulch over the weekend, given that it had the bonus honour weekend on. While I suck royally at PvP, it was still a decent amount of fun, and I even managed to get started saving some honour for some welfare epics Season One gear.
If you fancy a different kind of change, plenty of MMOs offer free trials. WoW offers a 10-day trial, if you're not one of the 10 million strong army that Blizzard is raising. Sony Online Entertainment have free trials available for Everquest, Everquest 2 and Star Wars Galaxies. Be warned that these downloads may well be rather large – I grabbed the Galaxies one a while back, and it took me around 12 hours to get it all downloaded and patched up. It's a shame that I haven't logged on yet.
Why not try your hand at a little RP? I know one good source of pointers for RP in WoW. It might be a little easier to get into if you happen to have a character on an RP server already, but if you don't, it's not like it's really tough to roll up a new character is it? Everquest 2 has a few RP servers and some good pointers on the official forums for new RP-ers. As far as I'm aware, Galaxies doesn't have any dedicated RP servers, although it does have a thriving RP community.
Finally, you could of course ignore any of the suggestions I've given here today, and go do something completely different. I'm repeating myself, I know – but it really does do some good to step out of our comfort zone every once in a while, it can be scary and unnerving, but it can also challenge us to think differently and try things you wouldn't normally have dared to try.