2 added 1735 characters in body

Okay, here's a much longer version (247 characters) that does full-on formatting of the output:

c,h,i,j,n,d,w[99];char s[99][99];main(r){for(scanf("%d%d",&n,&r);d=r;n=d)
h+=w[c++]=sprintf(s[c],"%d + ",n/d,r=n%d);for(;j+=w[i],i<c-1;puts(""))
for(printf("%*d\n%*s",j+(r=h-j)/2,1,j,s[i++]);--r;printf("-"));
s[i][w[i]-2]=0;printf("%*s\n",j-1,s[i]);}


Some examples of its output:

$echo 89 150 | ./cfr 1 0 + --------------------------- 1 1 + ----------------------- 1 1 + ------------------- 1 2 + --------------- 1 5 + ----------- 1 1 + ------- 1 1 + --- 2$ echo 151 8919829 | ./cfr
1
0 + ----------------------------
1
59071 + --------------------
1
1 + ----------------
1
2 + ------------
1
1 + --------
1
1 + ----
21
$echo 293993561 26142953 | ./cfr 1 11 + --------------------- 1 4 + ----------------- 1 14 + ------------ 1 4410 + ----- 104  Okay, here's a much longer version (247 characters) that does full-on formatting of the output: c,h,i,j,n,d,w[99];char s[99][99];main(r){for(scanf("%d%d",&n,&r);d=r;n=d) h+=w[c++]=sprintf(s[c],"%d + ",n/d,r=n%d);for(;j+=w[i],i<c-1;puts("")) for(printf("%*d\n%*s",j+(r=h-j)/2,1,j,s[i++]);--r;printf("-")); s[i][w[i]-2]=0;printf("%*s\n",j-1,s[i]);}  Some examples of its output: $ echo 89 150 | ./cfr
1
0 + ---------------------------
1
1 + -----------------------
1
1 + -------------------
1
2 + ---------------
1
5 + -----------
1
1 + -------
1
1 + ---
2
$echo 151 8919829 | ./cfr 1 0 + ---------------------------- 1 59071 + -------------------- 1 1 + ---------------- 1 2 + ------------ 1 1 + -------- 1 1 + ---- 21$ echo 293993561 26142953 | ./cfr
1
11 + ---------------------
1
4 + -----------------
1
14 + ------------
1
4410 + -----
104

1

## C, 119 characters

n,d,r;main(i){for(scanf("%d%d",&n,&d);r=n%d;n=d,d=r,i+=5)
printf("%*d\n%*d + ---\n",i+5,1,i,n/d);printf("%*d\n",i,n/d);}


Here are some examples of output:

$echo 15 98 | ./cfrac 1 0 + --- 1 6 + --- 1 1 + --- 1 1 + --- 7$ echo 98 15 | ./cfrac
1
6 + ---
1
1 + ---
1
1 + ---
7
\$ echo 98 14 | ./cfrac
7


While the truncated fraction line isn't as pretty-looking as some of the examples here, I wish to point out that this was a common technique for formatting continued fractions back in the days before desktop computers were ubiquitous.