Sky & Telescope did a piece recently on near approaches by near-by stars in the next few millennia and I've dug up the original research that was based on...

Astronomical Journal v. 117, no. 2, pp 1042

...which makes for an interesting read. The nearest approach (1.1 ly) will be by Gl 710 in ~ 1.4 Myr, but some old favourites get a lot closer relatively soon.

Barnard's dips in as close as 3.73 ly in just 9,700 years.

Alpha Centauri will get as close as 3.1 ly in ~ 27,000 years.

Lalande 21185 dips in to 4.7 ly in 20,000 years.

...so expect a few changes in millennia to come. The article also looks back a few million years and there are, suprisingly, no close approaches in the last 8 megayears - unless it zipped past at ultra-velocity. Algol got as close as 7.8 ly [!] some 6.9 Myr ago, but nothing major in historical times.