If it's just for sewing, the plastic folding tables are handy to have around. I got one from Office Depot that has legs that will adjust every 2", which is nice. It was more expensive than the ones I saw elsewhere, but on those, there weren't many height options with the legs. There are some portable ones with inserts that will allow your machine to sit down inside it, making it easier for quilting. They are small though and you'd probably need to put it up against another table for quilting. If you are looking for a furniture type of table, there are many, some pretty expensive. I saw one at my LQS that was around $1800.
There are a bunch on this site. I haven't purchased a table there, but I think I have purchased feet for my machines there.
http://www.sewvacdirect.com/deluxe-p...FQSxnQodoHQAEA