I once bought a miniature altar for a friend of mine who can't be very outwardly pagan at home. It came in a little tin that used to hold mints and everything, right down to the impossibly small besom, was handmade. (Well. except the candle, which, adorably, was a white birthday candle.) I miss my altar when I have to leave it and go home for the short breaks from school. There's just no time to set it up and tear it down again for a five-or-so day weekend. I have to say a tiny travel altar is pretty awesome. Only, I don't have one...
But I do have small things that I keep on me. That gets updated whenever needed and for whatever reason. Currently, I carry with me two pieces of quartz -- one is a heart and one is a singing crystal. For finals week, I also carried the Apophyllite crystal that the owner of The Fey Dragon gave me.
To work, I carry a Helm of Awe sigil, even after my workstudy boss switched. It protects just as it was made to, and has been nothing but helpful.
There's also jewelry, right? I wear my Thor's Hammer necklace pretty much daily. I used to cycle it out between a pentagram, a triquetra, a rune circle and a valknut -- but over time the Mjollnir (as its runes spell it) has been the one I feel most protected by. I also have a new necklace -- well, newer -- that is a Pictish Designs pebble with a raven on it. It was blue when I bought it, but over time it darkens. I wear this at all times except for showers. This holds a lot of my own personal energies; waking, sleeping and meditative. I recently aquired a wooden ring (since I have had trouble with my skin vs metals lately) that reads "Victory" in runes, with a Wunjo rune on the inside. I wear that when I remember. It has been such a long time since I was able to wear rings comfortably.
I know there are some people who carry around herbs with them in one way or another. I always think to make tiny spell bottles to bring along, but I haven't had a need for one myself yet. I did give a bottle of dried lavender to a friend; she needed to bring balance both to her own emotions and the areas she travelled through.
But the point being -- even if you can't have your altar around all the time, there are ways to bring some of it along. For me, that still reminds me that my path means combining the mundane with the metaphysical. I wouldn't be me if I seperated the two entirely.